1999 AMC 8 Problems/Problem 14

There is a rectangle present, with both horizontal bases being units in length. The excess units on the bottom base must then be 8. The fact that and are equal in length indicate, by the Pythagorean Theorem, that these excess lengths are equal. There are two with a total length of units, so each is units. The triangle has a hypotenuse of 5, because the triangles are right triangles. So, the sides of the trapezoid are , , , and . Adding those up gives us the perimeter, units.