A rectangular pool is 7 feet wide. It is 3 times as long as it is wide. Find the perimeter of the pool.

The answer is 56 ft

The perimeter of the rectangle with width w and length l is:

P = 2w + 2l

We know:

w = 7 ft

l = 3w = 3 * 7 = 21 ft

P = 2w + 2l

P = 2 * 7 + 2 * 21

P = 14 + 42

P = 56 ft