Math

Quote:

A picture 4 in. tall and 9 in. wide is to be scaled to 2.5 in tall. How wide should the smaller picture be for two pictures to be similar

similar means if you scale the height by some amount you need to scale the width by the same amount.

The height scale factor is the new height divided by the old one i.e. (2.5)/4

The new width will be the old width times this scale factor

A picture 4 in. tall and 9 in. wide is to be scaled to 2.5 in tall. How wide should the smaller picture be for two pictures to be similar

You can set up a proportion for this problem:
4 over 9 = 2.5 over x.
Since the two sides are equal, you can cross-multiply.
So 4*x = 9*2.5
Simplify.
4x = 22.5
divide both sides by 4 to find x, which is the width of the smaller picture.

To check your answer, the ratio of height to width should be the same for both pictures.
So 4 divided by 9 should equal 2.5 divided by your answer:)

Rom beat me to it