A rectangle has a measurement of 15 cm long and 9 cm wide. Label another rectangle that is similar and why are they similar?

Answer 1

pick any rectangle whose sides are the same multiple of 9 and 15

for example, .9 and 1.5
or 90 and 150

they are similar because that's what similar means: corresponding sides are in the same ratio.

corresponding angles are equal, because both figures are rectangles.