CPM Homework Help : GC Problem 7-86

A trapezoid with horizontal parallel bases: bottom is 8, and top is 13. Left side is 5 and right side is blank. A dashed line, labeled 4, is perpendicular to both bases, connects the bases. Find the area and perimeter of the trapezoid at right.

Hint:

Don't assume the trapezoid is isosceles even though it looks like it.
Start by solving for $x$ in the diagram, then solve for $y$ , then find the length of the unknown side of the trapezoid.

Split the trapezoid into parts. The base of the triangle on the left side is x. The length of the rectangle in the middle is 8. The width is 4. The base of the triangle on the right side is y. The hypotenuse is unknown.

Answer:

$\text{Area}=42\; \text{square units}$