public Quantity<U> zoomBy(double zoom) {
		return new Quantity<U>(value * zoom, unit);
	}
@Test
    public void zoomQuantity() throws Exception {
        Quantity<Metrics> q = new Quantity<Metrics>(100, Metrics.cm);
        assertThat(q.zoomBy(0.5)).isEqualTo(new Quantity<Metrics>(50, Metrics.cm));
    }