1982 AHSME Problems/Problem 10
Problem
In the adjoining diagram, bisects , bisects , and is parallel to . If , and , then the perimeter of is
Solution
Since and are angle bisectors of angles and respectively, and similarly . Because and are parallel, and by corresponding angles. This relation makes and isosceles. This makes and . + = 12, and + = 18. So, + = 12, and + = 18, and those are all of the lengths that make up . Therefore, the perimeter of is . The answer is .