When Are Two Rectangles Similar?

For two rectangles to be similar, their sides have to be proportional (form equal ratios). The ratio of the two longer sides should equal the ratio of the two shorter sides. However, the left ratio in our proportion reduces. We can then solve by cross multiplying.

What's similar to a rectangle?

The Square

A square also fits the definition of a rectangle (all angles are 90°), and a rhombus (all sides are equal length).

Under what conditions are two Rhombi similar?

Explanation: Two shapes are similar to each other if they are the same except for differences in scaling. This means that all of the angles of one shape have to be the same as the angles of the other shape, and all the sides have to be proportional to each other.