Question

A rectangle is shown. 2 right triangles sit on the top of the rectangle. The sides of the rectangle are congruent with 2 sides of the rectangle and have length x.
Which expression can be used to find the area of the composite figure?

4x
2x + 2x2
x2 + 2x
3x2

Answer 1

3x^2

Reason: The rectangle has height x and width 2x, so its area is 2x^2. Each right triangle has area (1/2)x·x = (1/2)x^2, so the two triangles together have area x^2. Total area = 2x^2 + x^2 = 3x^2.