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# Questions Asked onNovember 16, 2011

1. ## geometry

What happened when two fruit companies merged?

2. ## math

jose said all of the multiples of 8 are also multiples of 2. jamila said that all of the multiples of 8 are also multiples of 4. who is correct. Explain

3. ## physics

A box and its contents have a total mass M = 9 kg. A string passes through a hole in the box, and you pull on the string with a constant force F = 77 N (this is in outer space; there are no other forces acting). (a) Initially the speed of the box was vi =

4. ## Physics

A 49.0 g marble moving at 2.20 m/s strikes a 22.0 g marble at rest. What is the speed of each marble immediately after the collision?

5. ## English; conmas

Where should commas be placed? Combine flour shortening pecans and cold water to make a tasty pie crust.

6. ## physics

A 34-pound crate is pushed across the floor by a 30-pound horizontal force F1. Aside from the pushing force and gravity F2, there is also a 34-pound force F3 exerted upward on the crate and a 20-pound frictional force F4 What kinds of work do the force F1,

7. ## Chemistry

Complete the table by filling in the formula for the ionic compound formed by each pair of cations and anions, as shown for the first pair. Ion K+ NH+4 Mg2+ Fe3+ Cl- OH- CO3 2- PO3- 4 Complete the fourth row of the table.

8. ## math

What might you have if you don't feel well? letters are e, g, o, v, o, s, n, l

9. ## chemistry

Assuming that the total volume does not change after 0.200 g of KCl is added to 1.0 L of a saturated aqueous solution of AgCl, calculate the number of moles of Ag+ ion in the solution after equilibrium has been reestablished. For AgCl, Ksp = 1.8 × 10¯10

10. ## Physics

Because of the pressure inside a popcorn kernel, water does not vaporize at 100°C. Instead, it stays liquid until its temperature is about 175°C, at which point the kernel ruptures and the superheated water turns into steam. How much energy is needed to

11. ## chemistry

calculate the numbers of moles of sodium thiosulfate (Na2S2O3) and hence the moles of S2O3^2- ions present in the volume of 43mL someone plz help

12. ## Physics

Two children hang by their hands from the same tree branch. The branch is straight, and grows out from the tree trunk at an angle of 27.3° above the horizontal. One child, with a mass of 40.8 kg, is hanging 1.24 m along the branch from the tree trunk. The

13. ## Science

Which of the following is visible to a person only because light from another source reflects off it? - lightning - flashlight - cloud - sun

14. ## Calculus

this homework is due in one hour and i have no idea how to answer these questions. 1. A car is traveling at 50 mi/h when the brakes are fully applied, producing a constant deceleration of 20 ft/s^2. What is the distance covered before the car comes to a

15. ## Calculus

(a) Find the Riemann sum for f(x) = 7 sin x, 0 ≤ x ≤ 3π/2, with six terms, taking the sample points to be right endpoints. (Round your answers to six decimal places.) I got 3.887250 as an answer, but that's not right. (b) Repeat part (a) with

16. ## emergency physics

A 15 g bullet strikes and embeds in a 2.8 kg block suspended at the end of a 1 m string. After the collision the string rises to a maximum angle of 20 degrees to the vertical. what is the speed of bullet?

17. ## HISTORY

ISNT THIS RITE? With regard to British influences on India, which of the following statements is true? A. A primary objective of British rule was attaining food self-sufficiency for Indians. B. The common name for the British Indian Empire was the "British

18. ## physics

Because of the pressure inside a popcorn kernel, water does not vaporize at 100°C. Instead, it stays liquid until its temperature is about 175°C, at which point the kernel ruptures and the superheated water turns into steam. How much energy is needed to

19. ## algerbra

A ride in a cab costs $0.40 plus$0.15 per mile. a.Write an equation for traveling x miles in the cab.

20. ## algebra

one half the distance from boston to new york minus 25

21. ## chemistry

how many kg of chalcopyrite is needed to obtain 500g of pure copper

22. ## chem

In an experiment 4.0 g of ferrous ammonium sulphate, FeSO4.(NH4)2SO4.6H2O, is used. Since the oxalate in in excess, calculate the theoretical yield of the iron complex?

23. ## Geometry

the prerimeter of abcd is 92cm. ad is 7 more than twice ab. find the length of all four sides.

24. ## chemistry

calculate the numbers of moles of sodium thiosulfate (Na2S2O3) and hence the moles of S2O3^2- ions present in the volume of 43mL can someone plz help me?

25. ## Physics

A playground merry-go-round (which can be modeled as a disk) has a 3.4 m diameter, a mass of 240 kg and is rotating at 22.5 rpm. A 35 kg child running at 6.0 m/s, tangent to and in the same direction as the merry-go-round is turning, jumps on the outer

26. ## chemistry

would the molar mass of a volatile liquid be incorrectly high, incorrectly low or unaffected if a)you did not completely vaporize the liquid when you heated it. b)the foil cap got wet while you were cooling the flask and its contents with running water c)

27. ## chemistry

a steel cylinder with nitrotgen hydrogen and ammonia gases is at 500C and 5.00 atm if patrtila pressure of nitrogen is 1850 mm Hg and hydrogen is 1150 mm Hg what is the partial pressure of ammonia in mm H

79. ## chemistry

human body is 255 square inches what is the total weight of the atmosphere on a human body expressesd in pounds

80. ## Physics

The wave function for a certain standing wave on a string is given by y(x,t) = A0 sin(k0x)sin(ù0t) where k0 = 3ð rad/m and ù0 = 6ð rad/s . What is the wavelength of the standing wave?

81. ## physics

A college student is at a concert and really wants to hear the music, so she sits between two in-phase loudspeakers, which point toward each other and are 60.8 m apart. The speakers emit sound at a frequency of 428.75 Hz. At the midpoint between the

82. ## physics

Using Newton's Law of Universal Gravitation, compare the weight of a 68.1 kg astronaut on the surface of the earth to the gravitational pull of the Earth on the same astronaut when she is on the International Space Station. Constants: Average altitude of

83. ## Algebra 2

The problem is 3x^2 - 26 + 35 (We have to factor it!) So, I did the problem, but I'm not sure how to write the final answer. This is what my problem looks like so far: 3x^2 - 26 + 35 (3x^2-21x)-(5x+35) 3x(x-7)-5(x+7) and this is where I have the problem. I

84. ## human resources, (compensation and benefits)

Which competitive pay policy would you recommend to an employ? Why? Does it depend on circumstances faced by the employer? Which ones?

86. ## physics

a horizontal force of 60.0 N is exerted on a 2.00 kg discuss as it is rotated uniformily in a horizontal circle (at arm's length) at radius of 1.00 m. Calculate the speen of the disuss

87. ## English

The following lines are from Alexander Pope's "An Essay on Criticism." In it, Pope (1688-1744) gives his opinions on the secret of good writing, opinions that were very consistent with his times. Answer all questions based upon these lines. Those RULES of

88. ## Government US

What is an advantage in electing judges? a. Judges are more responsive. b. Judges are more independent. c. Judges are more competent. d. Judges are both more independent and more competent. I would say D ?

89. ## Science

Caleb is holding a metal block in his hand. What could he do to decrease the thermal energy of the block? a) cool it b) drop it c) hit it d) melt it

90. ## physics

A uniform rod (AB) of mass 80kg and 1.0m lenght is supported on the 2 knife edges placed 15.0cm from its ends. what will be the reactions at these support when a 20kg mass is suspend 10cm from the mid-point of the rod.(workings and diagram)

92. ## MATH

i need this as quick as possible please Omar is building a straight fence, with posts one meter apart. If the fence is 13 meters long, how many fence posts does he need? If the fence is 13 meters long, how many fence posts does he need?

93. ## physics

The drawing shows a boat being pulled by two locomotives through a canal of length 2.50 km. The tension in each cable is 5.00 103 N, and è = 19.0°. What is the net work done on the boat by the two locomotives?

94. ## algerbra 1

4. Your profit P is determined by subtracting the cost C, the amount of money it costs to operate a business, from the revenue R, the amount of money you earn from selling your product. Profit can be represented algebraically by the equations: Profit =

95. ## Trigonometry

How do you solve these equations algebraically? y=x^2+4x 2x-y=1 y=x^2+2x+3 x+y=1

97. ## mecs101

discuss a modern middle eastern country's attempt to either codify or replace shariah law.

98. ## chemistry

why is this statement false? "when an ionic compound dissolves in water an equal number of positive and negative ions is created."

99. ## english

Last night, Lucy and Neil met Morey in Gramercy Park. The predicate of the sentence is A. in. B. Morey. C. met. D. Lucy and Neil.

100. ## physics

the driver of a 1200kg car travelling 45km/h west on a slippery road applies the brakes, skidding to a stop in 35m. Determine the coefficient of friction between the road and the car tires

101. ## Social Studies

I have this assignment for ss that is due on monday. Here it is (the assignment paper) LETTER TO QUEEN ISABELLA In 1492, Queen Isabella of Spain provided an Italian explorer and navigator, Christopher Columbus with 3 small ships the Nine, The Pinta, and

102. ## Physics

The shaft of a pump starts from rest and has an angular acceleration of 3.40 rad/s2 for 11.0 s. (a) At the end of this interval, what is the shaft's angular speed? rad/s (b) What is the angle through which the shaft has turned

103. ## statistics

Let x be a random variable that represents the length of time it takes a student to complete a take-home exam in Dr. Larson’s psychology class. After interviewing many students, it was found that x has an approximately normal distribution with mean µ =

104. ## VB

I am new here; say to everyone first. Here is the a question for coding list box; it has two part: first part: Create a project that stores personal information for a little electronic "black book"; the fields in the file should include name, phone number,

Is there any sites for middle or high schoolors can do for computer clubs like any sites on making fun videos or movies, making amnination, putting drawing into computers to make your own comic books (girls and boys), ways to make a websites or a video

106. ## college chemistry

What is the ratio of KC2H3O2 and HC2H3O2 in a buffer with a pH of 5.25? Ka = 1.8 x10-5?

107. ## Physics

A curve of radius 55 m is banked so that a car of mass 1.5 Mg traveling with uniform speed 57 km/hr can round the curve without relying on friction to keep it from slipping on the surface.

Which competitive pay policy would you recommend to an employ? Why? Does it depend on circumstances faced by the employer? Which ones?

109. ## Physics

In the experiment, a meter is hooked up to a speaker to monitor the amplitude of the received sound. Suppose the background signal level is 15 mV, the signal is 90 mV with no attenuator and is 30 mV with an attenuator in place. Calculate pt/pi including

110. ## algerbra1

2. You are trying to decide how to most efficiently use your oven. You do not want the oven running at a high temperature when you are not baking, but you also do not want to waste a lot of time waiting for the oven to reach the desired baking temperature.

111. ## Art Apperciation

Compare Raphael’s School of Athens to Veronese’s Christ in the House of Levi. Explain how each artist reflected the political and social environment of Rome and Venice during the Renaissance period

How much power is generated by a 90 kg sprinter that accelerates up to 9.0 m/s in 2.8 seconds?

113. ## math

Who am I? I am a 4-digit number wih no two digits the same. My ones digit is twice my thousands digit. My hundreds digit is the diference between my tens and my thousands digit. My thousands digit is an odd number less than 6. I got one answer which was

114. ## Chemistry

For a lab experiment we have to draw the lewis structures of hydrides. 1) Carbon It asks for the formula of hydride. Total # of valence electrons and the lewis structure. Total electrons would be four. I am not sure what the formula would be or how to find

115. ## Science

Is it choice B....somebody please answer I really need to know An individual with the genotype Aa mates with an individual with the genotype AA. Which of the following is true? A) These two individuals will have four offspring. B) Half of the offspring

116. ## Technology in the Classroom

Which of the following scenarios most likely describes the future of technology in education?

117. ## physics

The sound level in decibels is typically expressed as β = 10 log (I/I0), but since sound is a pressure wave, the sound level can be expressed in terms of a pressure difference. Intensity depends on the amplitude squared, so the expression is β = 20 log

118. ## chemistry

calculate the number of moles of potassium iodate (KIO) that were present in the 5.00mL aliquot of standar potassium iodate solution Can someone please show me the workings to do questions like this one? thanks =]

119. ## physics

Using Newton's Law of Universal Gravitation, compare the effect of the Sun and the Moon on the tides. Constants: Mass of the Moon, M☽= 7.348E22 kg. Moon's semi-major axis, a☽= 3.844E8 m. You can find the other constants you will need on the Astronomy

120. ## physics

To show your friends how strong you are, you start pushing a big container with mass 50 kg along a long, flat highway. While you are pushing the container in a horizontal direction with an average force 350 N, it moves with acceleration 1 m/s/s. After 5

A horizontal spring with a spring constant of 200.0 N/m is compressed 25.0 cm and used to launch a 3.00 kg block across a frictionless surface. After the block travels some distance, the block goes up a 32 degree incline that has a coefficient of friction

122. ## differential equations

Consider the 2nd order differential equation: x''(t)=-x-A(x^2-1)x'(t) x(0)= 0.5 x'0)= 0 ''= 2nd order,'= 1st order where A is a positive constant.As the value of A increases this equation becomes increasingly stiff. Convert this equation to two first-order

123. ## Algebra II

The number of oscillations made by a pendulum in a given time is inversely proportional to the length of the pendulum. A certain clock with a 20-in.-long pendulum is losing 11.00 min/day. Should the pendulum be lengthened or shortened, and by how much?

124. ## math

a drawer contains n socks, of which 16 are striped. two socks are pulled from the drawer in the dark. waht is the largest possible value for n if the probability that both socks are striped that 1/2

125. ## Physics

If a&b are vectors such that a+3b=-3i+j & a-b=i-2j then find vectors a&b.

126. ## Algebra

A person rolls two dice. What are the odds against throwing at most a six?

127. ## chemistry

Volume of Na2S2O3(aq) required? final burette reading trial1= 45.00 trial2= 44.27 trial3= 45.28 initial burette reading trial1= 0.52 trial2= 1.22 trial3= 2.33 volume of Na2S2O3 used in each trial? average of the two volumes agreeing within 0.10mL? can

128. ## physics

Tarzan, played by Patrick Huard, 60 kg, must cross a stream 5 m wide, and full of hungry crocodiles. To do this, decides to slide along a sloping tree trunk, hollowed and moist so that there is no friction. After the trunk, there is a part of 3 m platform

129. ## physics

can someone explain how to do this step by step i already have the answer but i need to know how to do it!! the answer is (a)6.67m/s (b)111km/s^2 The muzzle velocity of 50g shell leaving a 3kg rifle 400m/s(a)What is the recoil velocity of the rifle?(b)If

130. ## algebra

Eight times the opposite of a number is 36 less than the product of 4 and the number. What is the number?

131. ## physics

The sound level in decibels is typically expressed as β = 10 log (I/I0), but since sound is a pressure wave, the sound level can be expressed in terms of a pressure difference. Intensity depends on the amplitude squared, so the expression is β = 20 log

132. ## physics

A hockey player is skating at 17 m/s comes to a complete stop in 2 m. What is the acceleration of the hockey player ?

133. ## Chemistry

What is the mass of 14 liters of gasoline? Assume that the density of gasloine is .680 grams per cubic centimeter. Provide answer in kilograms.

134. ## physics

the relative density of an alloy is 6.5.find the mass of the solid alloy cube of side 20cm.what volume of the alloy has a mass of 13kg

135. ## Physics

A 16,000 kg F-18 (jet fighter) lands at 52 m/s on an aircraft carrier, its tail hook snags the cable to slow it down. The cable is attached to a spring with a spring constant of 60,000 N/m. How far does the spring stretch to stop the jet?

136. ## physics

An airplane passenger carries a 250 N suitcase up the stairs, a displacement of 4.70 m vertically, and 5.30 m horizontally. How much work does the passenger do?

137. ## algerbra

Need help with this question I can get it. Bayside insurance offers two health plans, under A Giselle would pay the first $50 of her medical bills plus 35% of the rest. Under planb Giselle would$180 in bills. Giselle would save with plan B if she had more

138. ## science

if you lived in the southern hemisphere about the same distance from the equator as new jersey what seasons would you have and when

139. ## chemistry

calculate the number of moles of potassium iodate (KIO) that were present in the 5.00mL aliquot of standar potassium iodate solution Can someone please show me the workings to do questions like this one? thanks =]

140. ## basic english

In which of the following sentences is the underlined word an object pronoun? A. We returned our books to the library. B. You really should apologize to her. C. I would like you to listen to me. D. I gave her a gift for her birthday

141. ## statistics/psyc

Researchers are interested in the effectiveness of a particular treatment for insomnia. Fifty insomnia sufferers who responded to a newspaper ad are contacted, and each is given a pill with instructions to take it before going to sleep that night. The pill

142. ## physics

Using the weight equation, weight = (mass)(strength of gravity field) or Fg = mg, calculate your mass in kilograms. Constants: Strength of the gravity field near the surface of the earth, g = 9.8 m/s2. 4.448 Newtons equals one pound of force. You can find

143. ## Algebra II

The force of attraction between the earth and some object is called the weight of that object. The law of gravitation states, then, that the weight of an object is inversely proportional to the square of its distance from the center of the earth. If a

144. ## Algebra II

Assuming that y varies directly as the fourth power of x, fill in the missing values in the table of ordered pairs. x 18.3 74.5 ? y 29.6 ? 155

145. ## Language

The word "slippery" almost feels slippery! This may have to do with the blending of "s" and "I" so that the word glides or slips out of your mouth. Many English words seem to imitate their meaning. Try to record at least six such words.

146. ## math

Help with this word problem please! Bayside Insurance offers two health plan A, Giselle would have to pay the first $80.00 of her medical bills, plus 25% of the rest. Under plan B, Giselle would pay the first$90.00 but only 20% of the rest. For what

147. ## math

Solve for the value of x using mental math.1/4x = 1/4

148. ## Engineering

A 2kg piece of gold metal at 90 C is placed in 5 liters (=5kg) of water at 30 C. Determine the final temperature (Tf).

149. ## physics

can someone explain how to do this? The muzzle velocity of 60g bullet leaving 4kg rifle is 500 m/s towards the east. What is recoil velocity of the rifle?

150. ## math

Help with this word problem please! Bayside Insurance offers two health plan A, Giselle would have to pay the first $80.00 of her medical bills, plus 25% of the rest. Under plan B, Giselle would pay the first$90.00 but only 20% of the rest. For what

151. ## Algebra 2

is 4y(squared)-17y+15 factorable? i think its just not factorable, but i'm not sure. thank you::)

152. ## algebra

During the first part of a trip, a canoeist travels 69 miles at a certain speed. The canoeist travels 2 miles on the second part of the trip at a speed 5 mph slower. The total time for the trip is 3 hrs. What was the speed on each part of the trip?

153. ## algebra

11-(3x-6)+2(4x+5)-7x

154. ## Spanish

Could you please check these-I had to answer the questions. 1.¿Bailaste ayer? Sí,yo bailé ayer. 2.¿Caminaste a la escuela hoy? Sí, yo caminé a la escuela hoy. 3.¿Visitaste a tus primos el domingo pasado? Sí, yo visité a mis primos el domingo

155. ## CHemistry

Given that the half life of c 14 is 5,700 ,use the method c 14 dating to determine the age of a fossil if it has 25% of c 14 compared to living specimen.

156. ## math

A classroom is 10 yards long.THE floor is being tiled with new tiles that are each 10 inches long.HOW MANY TILES ARE NEEDED TO MAKE 1 ROW the length of the classroom

157. ## calculus

Show that the equation;x+3sinx=2 has a root between x=0.4 and x=0.6 using newton raphson's formular only

158. ## math

Help with this word problem please! Bayside Insurance offers two health plan A, Giselle would have to pay the first $80.00 of her medical bills, plus 25% of the rest. Under plan B, Giselle would pay the first$90.00 but only 20% of the rest. For what

159. ## math

5x+negative13x+6x+4x

160. ## math

(from current question)14x+20y+negative17y+negative17x

161. ## physics

A college student is at a concert and really wants to hear the music, so she sits between two in-phase loudspeakers, which point toward each other and are 60.8 m apart. The speakers emit sound at a frequency of 428.75 Hz. At the midpoint between the

162. ## Algerbra1

1.You have recently found a location for your bakery and have begun implementing the first phases of your business plan. Your budget consists of an $80,000 loan from your family and a$38,250 small business loan. These loans must be repaid in full within

163. ## Ap us history

What was George washintons platform in the election of 1792

164. ## Math- Algebra 2

write in vertex form (by completing the square)y=4x2+40x+96

165. ## algerbra 1

The decimal notation for the fraction -9/16 is Round to the nearest hundreth Solve 5x+8x=78 The solution is x= Simplify the answer. Type an integer of decimal. Solve using the addition principle 9.5=p-9.2 The soluation is p=

166. ## chemistry

How many grams of Nitric oxide are required to produce 145g of nitrogen in this reaction: Al2O3(s)+6NO(g)---->5N2(g)+6H2o(l)

167. ## Physics Disaster

Had The Same Teacher For Physics And Ughh I Am Stuck. Notes Help Me A Lot So If Anyone Could Write A Few Or A Bunch Out That Would Be Awesome. I Am Not The Type Of A Person Who Minds Writing Down Notes;) Teacher Told Us About Work And That The Formula For

168. ## English

Hello. Please help me with a few language problems. 1)Is it possible to say a)There are good responses about these experts. b)These experts have good responses. c)These experts are well reputed. Meaning: The experts have a good reputation, they are well

169. ## Englsih due at 10:30

please proof read for any errors and correct them Thank The word Divorce can make a lot of people feel hurt, angry, and depressed. But for others, it can mean the end to a bad or abusive marriage. Many people do not like to talk about it, but it can put a

170. ## math

make a tally chart for the number of students in the third, fourth ,and fifth grade classes : 26,25,27,27,26,28,27.

171. ## English

I have included the sentences I was most doubtful about. 1) The ship was cheered and they left the harbour. They went below the prow (I think "kirk" is the archaic word for "prow") 2)The mariners were then caught (can you say "struck") in (not by) a

172. ## English- Due Soon

Please check for any errors and correct them. Thank You. The word Divorce can make a lot of people feel hurt, angry, and depressed. But for others, it can mean the end to a bad or abusive marriage. Many people do not like to talk about it, but it can put a

173. ## Physics Disaster XXP

Had The Same Teacher For Physics And Ughh I Am Stuck. Notes Help Me A Lot So If Anyone Could Write A Few Or A Bunch Out That Would Be Awesome. I Am Not The Type Of A Person Who Minds Writing Down Notes;) Teacher Told Us About Work And That The Formula For

174. ## Texas Government

Which of the following statements is the most accurate? a. Citizens expect the courts to be both neutral and responsive to public opinion. b. Citizens expect the courts to be neutral, but not responsive to public opinion. c. Citizens expect the courts to

175. ## Biology

Is urine normally found in bladder of fetal pig? Why or why not?

176. ## ALGEBRA

how many permutations are there of the following word. mathematics

177. ## physics

can some one explain how to do this The muzzle velocity of 60g bullet leaving 4kg rifle is 500 m/s towards the east. What is recoil velocity of the rifle?

178. ## Accounting

If you treat the day of the month as a number (March 12th is the number 12, April 4th is the number 4), what is the average value of the numbers that represent the 6 Tuesdays that fall after September 12, 2011?

179. ## accounting

what are some examples of long format reports? When might an accounting department or accounting firm use these reports?

180. ## Economics

Im trying to figure out my grade what would i need to get a c average in the class;39%,of my grade is is based on 3 assignments(i got so far 62%,80%,haven't done the last assignment yet), 3 exams each worth 20%( i got a 2%,40%, haven't taken the last one)

181. ## Physics need help

Find the unit vector perpendicular for the vector i+2j-4k in the xy-plane.

182. ## math

how to solve this problem: max min(x-y)..... here where the max have written, under it x>=0 is also given. also under min y>=0 is given. Also tell that is this is equals to min max(x-y) ? (same as above under max x>=0, under min y>=0 is given) x and y both

183. ## statistics

which is a valid probability function a) p(x) for x=0,1,2 b)p(x)=x/1 for 0,1,2 c) p(x)=x/2 for 0,1,2

184. ## math

what is 3x+2y=6

185. ## Chemistry

Name the complexes: [V(ox)(Cl)3]- [Cr(F)3(I)(H2O)2] Write the formula for each of the following coordination compounds. Diamminetetrahydroxochromte (II) ion Bisethylenediaminediiodomanganese (IV) ion I think the name for the first one is

186. ## Calculus(Pre)

Can you explain linear speen and angular speed

187. ## math

21/b = 147/105

188. ## com/150

Could you please tell me if this is a good thesis statement for an expository essay on the personal benefits and values that can be instilled from doing voluntary community service? The personal benefits and values that can be instilled from doing

189. ## chemistry

how to prepare 1M,50ml buffer solution by taking Na2HPO4 and NaH2PO4.

190. ## Chemistry

From the following gases, choose the one with the lowest density at 25 C and 5 atm: H2S, CO2, C2H2, C2H6, C2H4 The answer is C2H2, but I am not sure why. Can you explain this? Thank you very much.

191. ## algebra

For the sequence an=6+5*(n-1), its first term is__??__ ; its second term is__??__ ; its third term is__??__ ; its fourth term is__??__ ; its fifth term is__??_ ; its common difference d= __??__ .

192. ## psychology

Teenage mothers who are accustomed to existing on hamburgers, French fries, and cokes need to consider the nutritional needs of the child. Research has shown that a poor diet can: a. restrict the development of eye and hair color. b. produce prenatal

-(5x+5)-4+8x

194. ## geometry

a classroom is 10 yards long . the floor is being tiled with new square tiles that are each 10 inches long. how many tiles are needed to make 1 row the length of the classroom

195. ## Chemistry

For idometric titration of copper, why is HCl added to KIO3 and then titrated immediatedly? What would happen if iodine-thiosulfate titration was done in a highly acidic solution? If the copper reaction solution was basic, how would the iodine-thiosulfate

196. ## Statistics

a machine fills containers with a standard deviation of filling weights of 1.5. calculate the mean weight if only 4 % of the containers hold less than 19 ounces

197. ## psychology

when kevin started his car in the parking lot, he also turned on the radio to his favorite station. as he enetered the street next to the campus, he turned the radio up due to the increased background noise in the car. entering the highway, he again

198. ## Awards

What kind of awards do they give out in middle school. I got ciztenships (like headliners) student of the month pricpals and honor rolls achivemnt in certain subjects NJHS (for some u made it) that's it what else do they giv out? Im really curois

199. ## Algerbra 1

3. In your industrial oven, you bake two baking sheets with 12 scones each, two baking sheets with 20 cookies each, and one baking sheet with 2 scones and 10 cookies. a. Write an expression that illustrates the total cost of all baked goods in the scenario

200. ## math

what is the population density if your goldfish population was found in 20x30 sq inch rectangular aquarium?

201. ## Algebra 2

Solve the following equation for v: S = (-1/2)gt2 + vt

202. ## Math- Algebra 2

write in vertex form (by completing the square)y=4x2+40x+96

203. ## USA PoliScience

A majority of Americans believe the death penalty deters crime. a. yes b. no The other question was about Texas believing so. I would say Texans believe it will deter crime but over all majority of Americans do not.

204. ## Algerbra 1

Multiply (-23)(-10)

205. ## Physics

Suppose A=3i-2j+k, B=-i-4j+3k&C is a vector lying along x-axis with the property that A.(B+C)=0. Then find vector C.

206. ## math

how would you write this word problem as an equation? When the gas gauge on her car was on the 3/8 mark, Karen pumped 15 gal. of gas into the tank in order to fill it. How many gal. of gas does the tank in Karen's car hold?

207. ## Word search

What does unscramble to. It is foe thanksgiving

208. ## math

John and Maria had an 8 slice pizza. John ate 1/3 and maria ate 1/4. how much pizza was left?

209. ## english-kite runner

Hey so im reading the kite runner and i have to asnwer comprehension quesions n idk how to answer these questions...sparknotes kinda help but at the same time it doesnt. so can somebody help me. 1) How did Hassan come into Amir's life? What contrast is

210. ## math

Let f(x)-1/2x-5. The average rate of change from x = 11 to x = 27 equals _____.

211. ## math

Let f(x)-1/2x-5. The average rate of change from x = 11 to x = 27 equals _____.

212. ## math

Jenelle has a blue jug and a red jug, both containing water. The blue jug has 4 gallons and 1 quart of water in it, and the red jug has 2 gallons and 2 quarts of water in it. How much water is in both jugs?

213. ## Chemistry Disaster XXP

Hey. Just Started A New Unit In Chem And The Sad Thing Is That I Had A Sub And She Did Not Know Nothing About This Stuff. So If Anyone Could Write Some Notes For Me Here That Are Understandable That Will Be Able To Help Me With The Work I Have To Finish.

214. ## Texas Government

Campaign spending limits for state judicial races a. are mandatory. b. are voluntary. c. help Democratic candidates but hurt Republican candidates. d. have been effective in reducing campaign spending. I cannot find this answer. C and B are obviously not

n/2-5=15

216. ## Technology in the Classroom

There are several different hard drives available for a computer.Which of the following size hard drives is the largest?

217. ## math

what is the product of 5 plus 3

218. ## Technology in the Classroom

What is the ideal computer arrangement to use when you want to integrate computers directly into the classroom curriculum?

219. ## SOCIAL STUDIES

What school was founded in 1636 to train Puritain Clergymen and is the oldest instituion of higher learning in the US?

220. ## algebra

The sum of the digits of a two-digit number is eleven. If the digits are reversed, the new number is sixty-three less than the original number. Find the original number. Help? &explain how you got the answer please.

221. ## Chemistry

How much energy in kJ is required to raise a 1.75 kg block of gold from 25.0 C to 105.0 C? The specific heat of gold is 0.03083 cal/g C, but I don't know how to compute the answer to the question.

222. ## physics

Using Newton's Law of Universal Gravitation, compare the gravitational pull of the Sun on the Earth to the gravitational pull of the Moon on the Earth. Constants: Mass of the Moon, M☽= 7.348E22 kg. Moon's semi-major axis, a☽= 3.844E8 m. You can find

223. ## chemistry

A solution contains 33.3 g H3PO4 in 448 mL of solution. Calculate its molarity.

224. ## Math

find the missing value that will make ratios 51 to 18, ? to 6

225. ## grammar

peer editing acamic papers require critical thi nking skills and diplomacy. is it subject verb agreement

226. ## statistics/psych

Find TWO media examples of two types of correlations (explained below). You will have to do some research to find these. Next: (1) Find one media example (don�t make up your own) of a correlation that could be argued to be spurious (third variable).

y/3.5+15=17

228. ## spanish

Can you help me with grammar/making sure this is coherent? C: Hola mi amigo! Mi nombre es Chaney. Y tú? K: Hola Chaney. Mi nombre es Kory. C: Vale..De dónde eres? K: Soy de Haverford. Soy Americano. Y tú? C: Soy de Maryland. Soy americano también. K: A

asked by New help on spanish script
229. ## Physics

Which electromagnetic radiation can be used in space to detect low temperatures? Gamma Rays Infra Red Ultra Violet Or any of the others?

230. ## algera 1

lucy makes and sells photo albums her monthly expenses are 600$plus 2$ for each album she sells. her income for each album sold is 10\$ the inequality belowcan be used to find the least number of albums lucy should see so that her income is greater than

is this graphable??? y=x^2-4x-2

232. ## English

Thank you. I still have a few doubts. So both sentences are correct: 1) " the ship was caught in a violent storm, then by mist and snow" OR "the mariners were struck by a violent storm .." 2) The sun rose on the left out of the sea, shone bright over the

233. ## physics

a body of mass2kg is lying on a rough inclined surface of inclination 30 degree .find the magnitude of the force parellel to the incline needed to make the block move .1)up the incline .2)doun the incline. cofficent of static friction is 0.2

234. ## English

I urgently need you to revise this email. Thank you very much in advance. 1) My science colleague is willing to work on a project in English concerning ecology with some of her students in the years 10-11. 2) Though we haven't got a bilingual branch at the

235. ## physics

plzz help me with my homework!!! Tarzan, played by Patrick Huard, 60 kg, must cross a stream 5 m wide, and full of hungry crocodiles. To do this, decides to slide along a sloping tree trunk, hollowed and moist so that there is no friction. After the trunk,

236. ## Research topic, English

My research topic is Banning Use of Cell Phones While Driving (include calls and texts) Could you give me some ideas of research questions? I have to have three. I already have three but I am not sure if they are research questions. will banning cellphones

237. ## math

only 40% of people between the ages of 18 and 24 read the newspaper. what % of people reads the newspaper?

238. ## algebra

Average cost of a bicycle is modeled by the function c(x)=.1x^2-1.7x+10 where c(x) is measured in dollars. how many bicycles should be built in order to minimize the average cost per bicycle?

239. ## algebra

ÐºÐ°Ðº Ñ‡Ð¸ÑÐ»Ð¾ 42 Ð¿ÐµÑ€ÐµÐ²ÐµÑÑ‚Ð¸ Ð² ÑÑ‚ÐµÐ¿ÐµÐ½ÑŒ

240. ## English/Writing

This is for an essay: How do you say/phrase "he used to", "he does not", "he is confronted with", "he would rather", "they have evolved", and "have succeeded" in present tense?

241. ## math

How many 16ths is 87 1/2

242. ## entrepreneur

Can someone who is a leader not be a manager? Why or why not? Can someone who is a manager not be a leader? Why or why not?

243. ## math

An urn contains 5 red marbles, 4 blue marbles, and 3 green marbles. A marble is selected at random and then, without replacing the first marble, a second marble is selected at random. What is the probability of selecting a green marble and then a red

244. ## Current political issues in the US

Could any one help me name some current political issues here in the US? Thanks in advance!

-9-(12-3x)

246. ## math

how many teaspoon of water can fill a 6 centimeters tall glass?

247. ## chemistry

A solution of sulfuric acid in water that is 25% H2SO4 by mass has a density of 1178 g/ml. Which expression gives the molarity of this solution?

248. ## math

3a - 1 1/2 = -5 1/4

249. ## Math

Record 7 digits (0-9) in ascending order who has a mean of 3 and a standard deviation of 0. Thanks

250. ## algebra

Is the sequence an=8n-14 arithmetic? Your answer is (input yes or no)__??__ ; if your answer is yes, its first term is__??__ . its common difference is__??__ .

251. ## math

Record 7 digits (0-9) in ascending order whose mean, median, and mode are 1 and which have a standard deviation larger than 0. Thanks

252. ## magda

9.6/a = 0.8/0.6

253. ## Math

Record 7 digits (0-9) in ascending order that have an inter-quartile range of 4.

254. ## Math

Record 7 digits (0-9) in ascending order that have a mean of 3 and a median of 1. Explain how to come up with the answer as well please and thank you.

255. ## Algebra

(x+2)-(x-2)-12x =??

256. ## psychology

when kevin started his car in the parking lot, he also turned on the radio to his favorite station. as he enetered the street next to the campus, he turned the radio up due to the increased background noise in the car. entering the highway, he again

257. ## psychology

Describe bi-polar disorder in two ways: clinically (objectively) and emotionally (subjectively).

258. ## science

A push is an example of what?

259. ## arithmetic

If you treat the day of the month as a number (March 12th is the number 12, April 4th is the number 4), what is the average value of the numbers that represent the 6 Tuesdays that fall after September 12, 2011

260. ## Chemistry

Given that the 2008 concentration of CH4 in the atmosphere was 1.88 ppm, calculate the total mass of CH4 in the atmosphere in 2008. The total mass of the atmosphere was 5.1x10^18 kg and the average molar mass of the atmosphere is 29.0 g/mole

261. ## English

I am doing the 4 humours for english home work and have to give examples of characters from tv, film or book that match the 4 humours so melancholy, phlegm, sanguine and choler.

262. ## chemistry

4g of h2 reacts 70 g of ci2 and forms

263. ## Physics

A 822 kg car accelerates from rest to 101 km/h in 1.15s. What change in momentum does the force produce?

264. ## Math

Write each percent as a decimal and as a fraction in simplest form. 5/8% would be .625% how do I make 5/8% into a fraction, or do I make .625% into a fraction.

265. ## English

Do you think I should consider this sentence (1) as wrong? (I included it in a test) . 1) He tells how his ship was caught in a violent storm, then by mist and snow and finally was surrounded by ice. 2) I need to find a reading comprehension at

267. ## calculus

f(x)= −x2lnx find the critical points , increasing & decreasing interval and concavity.Please just show me the steps on how to get the increasing and decreasing interval and critical pts . Thanks :)

268. ## math

14x+20y+negative17y+negative17x

269. ## social studies

contribution of cesar beecana

270. ## American History

what policy did Roosevelt call for in his memo to fechner in 1935 pertaining to the CCC camps?

271. ## Social Studies

During Rutherford B. Hayes's presidential run, what's was bad or good about it?

272. ## math

(from current question)5x+negative13x+6x+4x simplify

273. ## algebra

Lawrence has planted a round flower garden in his back yard. The garden is 8 feet across. How many feet of fencing does Lawrence need to enclose the flower garden?

274. ## USA PoliScience

Which of the following state courts is a magistrate court? a. county b. district c. appeals d. municipal I would say municipal courts

275. ## Physics

planet orbits a star once every 2.84 10^7 s in a nearly circular orbit of radius 1.42 10^11 m. (a) With respect to the star, determine the angular speed of the planet. (b) With respect to the star, determine the tangential speed of the planet. (c) With

276. ## math

What is Bobby's number? It is between 15 and 25. If you subtract the tens digit from the ones digit, the difference is 8.

277. ## world history

What were the 5 major Greek city-states ? Sparta,Athens, Corinth,Argos,Megara Right?

278. ## pre algebra

my numerator is a prime number My denominator is divisible by 2 i am equivalent to 1/5

279. ## ETHNIC DIVERSITY

I am trying to locate credible information in regards to the following question. Please note, I do not want the answers, just possible locations that might provide me with a place to start looking as I can not find anything recent. According to research

write the next three numbers in the pattern; 0.75,15,300,____,_____,____?

281. ## media

Huge corporations own every television network and most other media outlets. How does this affect their news coverage? How much influence do you think these corporations have on the public? Do you think the public is aware of the comments made by you and

282. ## Chemistry :P

Hey. Just Started A New Unit In Chem And The Sad Thing Is That I Had A Sub And She Did Not Know Nothing About This Stuff. So If Anyone Could Write Some Notes For Me Here That Are Understandable That Will Be Able To Help Me With The Work I Have To Finish.

I have to put these in the past tense-Are they correct? 1. Tú hablas por teléfono. Tú habaste por teléfono. 2. Nosostros bailamos mucho los fines de semana. This would be the same in past tense, I think?? 3. Tú y yo cantamos los domingos. This would

284. ## Physics

A weight with mass m lies on a surface with no friction. The weight is also connected to a spring with springconstant k and then the weight is driven with outer force F(t)=F0sin(Ωt). There is a friction in the spring and he‘s described with –bv(t).

285. ## English

Could you please help me revise the rephrase of these sentences from Colerdige's The Ballad of the Ancient Mariner? 1) "The ship was cheered, the harbour cleared, Merrily did we drop Below the kirk, below the hill..." The ship was cheered and they left the

286. ## Technology in the Classroom

A software package that you would like to run on your classroom computer lists a 486 computer as a minimum requirement. On which of the following compputers would you expect the software to be able to run?

287. ## Soc 331

Discuss current trends affecting social welfare. Do modern trends favor the solution of social issues? What are the most effective social welfare organizations today in your opinion, and why? I think that modern trends do favor solution, but I'm not

288. ## chemisrty

what is the final concentration of a solution if 100mL of water is added to a 25mL of 5.0 M NaCl?

289. ## college alegebra

Can someone please help me!!!!!! Find th eequation of the line containing the point P and having the slope m. Write your answer in slope intercept form. Graph this line. P= (0,0) M = 0

290. ## Physics

A block of mass m = 5.2 kg is pulled up a è = 24° incline as in the figure with a force of magnitude F = 34 N.

8-x>4

292. ## health and social care

can you tell me about the nature vs nurture debate please thankyou

293. ## science

how many atoms are in a mole?

294. ## Physics

Suppose vectors a&b if a x b=c. Show that c is perpendicular to a&b. Please help me.

295. ## science

I'm like 90% sure the answer is B, am I correct? An individual with the genotype Aa mates with an individual with the genotype AA. Which of the following is true? A) These two individuals will have four offspring. B) Half of the offspring will be Aa. C)

296. ## Government US

Which of the following people are least likely to believe that money has too much influence on judges? a. lawyers b. judges c. citizens d. police Wouldn't it be judges themselves?

297. ## SCIENCE

The global water cycle provides renewable water, but a number of factors affect how much freshwater is available for human consumption. Describe these factors and circumstances.

298. ## science

If the conditions are above-freezing air inside a cloud and freezing air beneath it.What type of precipitation would this be?

299. ## government

Through the grants of power in the Constitution, the Framers sought to: (Points : 5) define the powers of state governments. create a government in which sovereignty was invested in the national government only. enumerate the rights of individuals. both

300. ## mecs

compare the formation of Islamic law to what you know of development of Western legal sytems?

301. ## middle east culture

what are some of the different ways that the shariah can be interpreted and applied to modern society?

302. ## Math61

R is bounded by Y=2x-x^2 and the x-axis. Find the centroid of R. Sketch the region.

303. ## English

I need synonymous and antonyms of 1) bluster 2) commentary 3) facet 4) synopsis 5) tarry 6) setback 7) fidelity I need this seven words to finish my homework . Pleaseeeee

304. ## math

Of the 50 state in the united state, 8 states have a population of one million people or fewer.Make a plan and write an addition equation to show that the sum of the state with more than one million people and the states whith one million people or fewer

305. ## math

What is the rule for finding coordinates after a 90 degree rotation? after a 180 degree rotation? after a 270 degree rotation?

306. ## math

how many digits can the product of 2 2 digit numbers have

307. ## Science

Which electromagnetic radiation can be used in space to detect low temperatures? Gamma Rays Infra Red Ultra Violet Or any of the others?

I have to put these in the past tense-Are they correct? 1. Tú hablas por teléfono. Tú habaste por teléfono. 2. Nosostros bailamos mucho los fines de semana. This would be the same in past tense, I think?? 3. Tú y yo cantamos los domingos. This would

309. ## Basic english

Which of the following statements is not true? A. "Whom" can serve as the object of a preposition. B. "Whom" is an object pronoun. C. "Who" and "whom" are personal pronouns. D. "Who" is a subject pronoun.

310. ## Science

Example of a concept map for potential energy

311. ## algebra

x-19y+1-3x+23y-16

312. ## Math

find the distance around a rectangular swimming pool with a width of 20 yd and a length of 25 yd


text:
## The Annals of Statistics

### Estimation Via Linearly Combining Two Given Statistics

#### Abstract

We consider the problems of (i) covariance adjustment of an unbiased estimator, (ii) combining two unbiased estimators, and (iii) improving upon an unbiased estimator. All these problems consist in determining a minimum dispersion linear unbiased combination of given two statistics, one of which is an unbiased estimator of a vector parameter $\mathbf{\theta} \in \mathscr{H}$, and the expectation of the other is a zero vector in the problem of covariance adjustment, is equal to $\mathbf{\theta}$ in the problem of combining, and is equal to a subvector of $\mathbf{\theta}$ in the problem of improving. The solutions obtained are substantial generalizations of known results, in the sense that they are valid for an arbitrary joint dispersion matrix of the given statistics as well as for the parameter space $\mathscr{H}$ being an arbitrary subspace of $\mathscr{R}^k$.

#### Article information

Source
Ann. Statist., Volume 11, Number 2 (1983), 691-696.

Dates
First available in Project Euclid: 12 April 2007

https://projecteuclid.org/euclid.aos/1176346173

Digital Object Identifier
doi:10.1214/aos/1176346173

Mathematical Reviews number (MathSciNet)
MR696079

Zentralblatt MATH identifier
0515.62053

JSTOR

format: plain


text:
Search by Topic

Resources tagged with Addition & subtraction similar to Hot Pursuit:

Filter by: Content type:
Stage:
Challenge level:

There are 68 results

Broad Topics > Calculations and Numerical Methods > Addition & subtraction

Hot Pursuit

Stage: 3 Challenge Level:

The sum of the first 'n' natural numbers is a 3 digit number in which all the digits are the same. How many numbers have been summed?

Chameleons

Stage: 3 Challenge Level:

Whenever two chameleons of different colours meet they change colour to the third colour. Describe the shortest sequence of meetings in which all the chameleons change to green if you start with 12. . . .

The Patent Solution

Stage: 3 Challenge Level:

A combination mechanism for a safe comprises thirty-two tumblers numbered from one to thirty-two in such a way that the numbers in each wheel total 132... Could you open the safe?

As Easy as 1,2,3

Stage: 3 Challenge Level:

When I type a sequence of letters my calculator gives the product of all the numbers in the corresponding memories. What numbers should I store so that when I type 'ONE' it returns 1, and when I type. . . .

Arrange the Digits

Stage: 3 Challenge Level:

Can you arrange the digits 1,2,3,4,5,6,7,8,9 into three 3-digit numbers such that their total is close to 1500?

Largest Number

Stage: 3 Challenge Level:

What is the largest number you can make using the three digits 2, 3 and 4 in any way you like, using any operations you like? You can only use each digit once.

Alphabet Soup

Stage: 3 Challenge Level:

This challenge is to make up YOUR OWN alphanumeric. Each letter represents a digit and where the same letter appears more than once it must represent the same digit each time.

Like Powers

Stage: 3 Challenge Level:

Investigate $1^n + 19^n + 20^n + 51^n + 57^n + 80^n + 82^n$ and $2^n + 12^n + 31^n + 40^n + 69^n + 71^n + 85^n$ for different values of n.

Digit Sum

Stage: 3 Challenge Level:

What is the sum of all the digits in all the integers from one to one million?

Kids

Stage: 3 Challenge Level:

Find the numbers in this sum

Score

Stage: 3 Challenge Level:

There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about. . . .

Multiply the Addition Square

Stage: 3 Challenge Level:

If you take a three by three square on a 1-10 addition square and multiply the diagonally opposite numbers together, what is the difference between these products. Why?

Jugs of Wine

Stage: 3 Challenge Level:

You have four jugs of 9, 7, 4 and 2 litres capacity. The 9 litre jug is full of wine, the others are empty. Can you divide the wine into three equal quantities?

Pairs

Stage: 3 Challenge Level:

Ann thought of 5 numbers and told Bob all the sums that could be made by adding the numbers in pairs. The list of sums is 6, 7, 8, 8, 9, 9, 10,10, 11, 12. Help Bob to find out which numbers Ann was. . . .

And So on and So On

Stage: 3 Challenge Level:

If you wrote all the possible four digit numbers made by using each of the digits 2, 4, 5, 7 once, what would they add up to?

Got it Article

Stage: 2 and 3

This article gives you a few ideas for understanding the Got It! game and how you might find a winning strategy.

Adding and Subtracting Positive and Negative Numbers

Stage: 3

How can we help students make sense of addition and subtraction of negative numbers?

Countdown

Stage: 2 and 3 Challenge Level:

Here is a chance to play a version of the classic Countdown Game.

3388

Stage: 3 Challenge Level:

Using some or all of the operations of addition, subtraction, multiplication and division and using the digits 3, 3, 8 and 8 each once and only once make an expression equal to 24.

Making Sense of Positives and Negatives

Stage: 3

This article suggests some ways of making sense of calculations involving positive and negative numbers.

I'm Eight

Stage: 1, 2, 3 and 4 Challenge Level:

Find a great variety of ways of asking questions which make 8.

Playing Connect Three

Stage: 3 Challenge Level:

In this game the winner is the first to complete a row of three. Are some squares easier to land on than others?

Tis Unique

Stage: 3 Challenge Level:

This addition sum uses all ten digits 0, 1, 2...9 exactly once. Find the sum and show that the one you give is the only possibility.

Cayley

Stage: 3 Challenge Level:

The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?

Eleven

Stage: 3 Challenge Level:

Replace each letter with a digit to make this addition correct.

Crossed Ends

Stage: 3 Challenge Level:

Crosses can be drawn on number grids of various sizes. What do you notice when you add opposite ends?

Magic Squares for Special Occasions

Stage: 3 and 4

This article explains how to make your own magic square to mark a special occasion with the special date of your choice on the top line.

Football Sum

Stage: 3 Challenge Level:

Find the values of the nine letters in the sum: FOOT + BALL = GAME

Have You Got It?

Stage: 3 Challenge Level:

Can you explain the strategy for winning this game with any target?

Pair Sums

Stage: 3 Challenge Level:

Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?

Pyramids

Stage: 3 Challenge Level:

What are the missing numbers in the pyramids?

2010: A Year of Investigations

Stage: 1, 2 and 3

This article for teachers suggests ideas for activities built around 10 and 2010.

Clocked

Stage: 3 Challenge Level:

Is it possible to rearrange the numbers 1,2......12 around a clock face in such a way that every two numbers in adjacent positions differ by any of 3, 4 or 5 hours?

Amazing Card Trick

Stage: 3 Challenge Level:

How is it possible to predict the card?

Pole Star Sudoku 2

Stage: 3 and 4 Challenge Level:

This Sudoku, based on differences. Using the one clue number can you find the solution?

Making Maths: Double-sided Magic Square

Stage: 2 and 3 Challenge Level:

Make your own double-sided magic square. But can you complete both sides once you've made the pieces?

Got It

Stage: 2 and 3 Challenge Level:

A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.

Weights

Stage: 3 Challenge Level:

Different combinations of the weights available allow you to make different totals. Which totals can you make?

Connect Three

Stage: 3 and 4 Challenge Level:

Can you be the first to complete a row of three?

Consecutive Numbers

Stage: 2 and 3 Challenge Level:

An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

Reach 100

Stage: 2 and 3 Challenge Level:

Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.

Aba

Stage: 3 Challenge Level:

In the following sum the letters A, B, C, D, E and F stand for six distinct digits. Find all the ways of replacing the letters with digits so that the arithmetic is correct.

An Introduction to Magic Squares

Stage: 1, 2, 3 and 4

Find out about Magic Squares in this article written for students. Why are they magic?!

First Connect Three for Two

Stage: 2 and 3 Challenge Level:

First Connect Three game for an adult and child. Use the dice numbers and either addition or subtraction to get three numbers in a straight line.

First Connect Three

Stage: 2 and 3 Challenge Level:

The idea of this game is to add or subtract the two numbers on the dice and cover the result on the grid, trying to get a line of three. Are there some numbers that are good to aim for?

Always the Same

Stage: 3 Challenge Level:

Arrange the numbers 1 to 16 into a 4 by 4 array. Choose a number. Cross out the numbers on the same row and column. Repeat this process. Add up you four numbers. Why do they always add up to 34?

Card Trick 2

Stage: 3 Challenge Level:

Can you explain how this card trick works?

Make 37

Stage: 2 and 3 Challenge Level:

Four bags contain a large number of 1s, 3s, 5s and 7s. Pick any ten numbers from the bags above so that their total is 37.

Cubes Within Cubes

Stage: 2 and 3 Challenge Level:

We start with one yellow cube and build around it to make a 3x3x3 cube with red cubes. Then we build around that red cube with blue cubes and so on. How many cubes of each colour have we used?

Top-heavy Pyramids

Stage: 3 Challenge Level:

Use the numbers in the box below to make the base of a top-heavy pyramid whose top number is 200.


text:
Electric field Fourier decomposition

I have the following decomposition for the electric component of light:

$$\renewcommand{\vec}[1]{\mathbf{#1}}\vec{E}(\vec r)=\frac1{4\pi^2} \iint_\Omega \vec A(k_x, k_y) \mathrm{e}^{i \vec{k} \cdot \vec{r}} \, \mathrm{d}k_x \mathrm{d}k_y.$$

Similarly, the magnetic field is: $$\renewcommand{\vec}[1]{\mathbf{#1}}\vec{H}(\vec r)=\frac1{4\pi^2} \iint_\Omega \frac{\vec k}{\omega \mu_0} \times \vec A(k_x, k_y) \mathrm{e}^{i \vec{k} \cdot \vec{r}} \, \mathrm{d}k_x \mathrm{d}k_y.$$

Fine, this is the setting. Now I wish to compute the average Poynting vector $\langle \vec S \rangle$:

$$\langle \vec S \rangle = \frac12 \operatorname{Re} [\vec E(\vec r) \times \vec H(\vec r)^*].$$ Is there a way to express $\langle \vec S \rangle$ in a nice form? Integrals of functions of $\vec A$ for example. I get horrendous expressions with convolutions that don't give me a nice compact formula.

I know that this might actually be more mathematics than physics, but it might be possible that the physical boundary conditions give a better solution.

-
I'll check Jackson's electrodynamics book and see if it says anything relevant, though if you are set on expressing $\langle S\rangle$ in terms of the momentum-space vector potential, it's possible you might not be able to do any better than a convolution. –  David Z Mar 2 '12 at 6:34
@David: I want an expression that is the least computationally expensive. If that has a convolution, then so be it :-). –  Jonas Teuwen Mar 2 '12 at 12:01
Convolution sucks, computationally; but there are always fourier transform tricks to save time. –  Colin K Mar 17 '12 at 19:43

You could potentially simplify this slightly further, were there any relations between $\bb{A}$ and $\bb{k}$. Going back to the coordinate expression for $\bb{S}$ will require another integration and will be no simpler than the original form you had given.


text:
# Categories

authors (intermediate)

## Purpose of categories

Categories? (also known as "tags") are a way to organize and find related pages. Categories are implemented by default in PmWiki, and in most wikis they don't require any special code or markup, they're just a useful convention. The idea is that every page that falls into a particular subject area should have a link to a shared page containing links to other pages on that subject. These pages are created in the Category group, and thus these subject areas are called "categories".

## Using categories

Getting categories to work requires a single step: adding links to each category. A category named Subject is created by adding a link to Category.Subject on any page. When you add the link to a page, the page can be described as being in the category "Subject".

There is a special markup for creating these links which makes categories work more smoothly: [[!Subject]] will create a link to Category.Subject. So [[!Subject]] is a kind of shortcut to the page Subject in the category group.

A Category.GroupFooter file is included in the PmWiki release that contains the line (:pagelist link={*$FullName} list=normal:) so that whenever a category page is displayed, it will show a list of links to pages that reference that page in the category group. Like any other page in wikilib.d you can modify this page and it will not get overwritten by another release. It is worth noting that rather than using Category.GroupFooter, the pagelist directive can be added to Category.GroupHeader to similar effect; it just depends on whether you'd prefer to have the list of pages appear before or after any text that you add to the individual category pages (which can be edited just like normal pages). Because we use the normal PageList link= markup, you can use it not only in the category group. If you want to show all pages belonging to the category Subject you can use on any wiki page (:pagelist link=Category.Subject list=normal:). Similarly, there's no requirement that a "category page" has to be in the Category group -- any page can define a "category" of pages that link to it. An administrator can override the default category group name of "Category" by setting the $CategoryGroup variable in config.php to another group name. (Normally a change such as this should be done during initial setup on a new wiki; changing this on a wiki with existing content can cause problems with pagelists unless each page with a category is re-saved.)

SDV($CategoryGroup,'Category'); Markup('[[!','<links','/$$$!([^\|$] ?)$$\]/', "[[$CategoryGroup/$1]]");  ## Coming up with good category schemes The hard part about using categories is choosing a good vocabulary. Site content managers may wish to follow the Guidelines for the establishment and development of monolingual thesauri (ISO 2788-1986) and the Guidelines for the establishment and development of multilingual thesauri (ISO 5964-1985). Questions to think about include: • whether a scheme already exists and can be reused • number of levels in a multilevel scheme (not too shallow, not too deep -- e.g. 3) • number of categories per page (not too many, not too few -- e.g. 3) • consistent use of singular ([[Mercury]] is a [[!planet]]) or plural ([[Mercury]] is in the [[!planets]] category) • disambiguation and use of phrases ([[!musical instruments]] and [[!medical instruments]]) or Cookbook:Subgroup Markup ([[!Instruments*Musical]] and [[!Instruments*Medical]]) Or you can just let people use whatever category terms they find meaningful. A vocabulary (or "folksonomy") will emerge over time. ## Showing a list of categories To show a list of categories we can use a pagelist for the pages in the category group. For instance the following will list pages in the Category group, put it on page Category.Category? for convenience, or on any other page: (:pagelist group=Category list=normal fmt=#title:) But there is a problem: Just adding a category markup to a page will not create a corresponding category page, even though following the link will show the page with a list of pages linking to it! To have category pages automatically created in group 'Category' add the following to config.php: $AutoCreate['/^Category\./'] = array('ctime' => $Now, 'text' => 'List of pages linking to {$Title}'); (note the quotes)

Change 'Category' to the name of your category group. You can also add more definitions for more category groups, useful if you use a recipe like Cookbook:Tagger which allows multiple category groups.

Note that categorizing a page (using the [[!category markup]]) cannot be distinguished from referring or linking to a category (using the normal [[link markup]]), i.e. pages referring to a category become part of that category. This is the subject of a long outstanding feature request that seems to be hard to implement without breaking other functionality. You can link to a category without categorizing the page by using an external link, such as: [[{Category.MyCategory\$PageUrl}|MyCategory]]. Since the link is external, all pages (not just the category page) will ignore it when listing backlinks.