A trapezoid is a quadrilateral with one pair of parallel sides.
The formula for the area of a trapezoid is
In the diagram above, the area of the trapezoid is
If two polygons are similar, then corresponding angles are equal, and corresponding sides are in proportion.
In the two rectangles above, the angles are all the same (all rectangles have four 90° angles), and the sides of the larger are 1.5
times the sides of the smaller. Therefore, these two rectangles are similar.