An equilateral triangle has a side length of 20 . If a square has the same perimeter as this triangle, the area of the square is
(A) 25
(B) 400
(C) 225
(D) 60
(E) 100
An equilateral triangle with a side length of 20 must have a perimeter of 60 .

A square with a perimeter of 60 must have a side length of 15.

A square with a side length of 15 must have an area of 225.

ANSWER: (C)