This the third part of the series on finding the area of a trapezoid. In the first post, we discussed the derivation of the area of a trapezoid and give a worked example. In the second post, we discussed how to find the area given the base and the height as well as to find the height given the area and the base.

In this post, we are going to find the base, given the height and the area. We continue with the fourth example.

**Example 4**

A trapezoid has area 65 square centimeters, height 13 cm, and base of 4 cm. Find the other base.

*Solution*

In this example, we have , and . We are looking for . Continue reading