How to find the perimeter of a polygon - PSAT Math
Card 0 of 1
Note: Figure NOT drawn to scale.
Refer to the above figure. The white trapezoid is isosceles. Give the perimeter of the blue polygon.
Note: Figure NOT drawn to scale.
Refer to the above figure. The white trapezoid is isosceles. Give the perimeter of the blue polygon.
The lower base of this trapezoid is 
units longer than the upper base, and being isosceles, it is symmetrical. As a result, the lower leg of the right triangle at bottom is half this difference, or 18, which is the same as the upper leg. That makes the right triangle isosceles, and, therefore, a 45-45-90 triangle. Subsequently, the hypotenuse, which is one leg of the trapezoid, has length 
times a leg of the triangle, or 
.
The blue polygon has two sides that are the legs of this isosceles trapezoid, both of which have length 
; its other three sides are of length 64, 50, 100, and 50. Add them:
The lower base of this trapezoid is
The blue polygon has two sides that are the legs of this isosceles trapezoid, both of which have length
Compare your answer with the correct one above