What is the perimeter of the walkway around the pool?

• A. 110 feet
• B. 118 feet
• C. 112 feet
• D. 120 feet

Answer: (B)

To find the perimeter of the walkway, think about the outer boundary formed when the walkway surrounds the pool. If the pool has length L and width W, and the walkway is w feet wide, the outer rectangle around the pool measures L + 2w by W + 2w. The perimeter of that outer boundary is 2[(L + 2w) + (W + 2w)] = 2(L + W) + 8w. In this problem, the numbers given lead to 2(L + W) + 8w = 118, so the walkway’s perimeter is 118 feet. This uses the outer boundary, not the inner edge of the pool. If you tried different values, you’d get a different outer perimeter, which wouldn’t match the problem’s measurement.