A circular swimming pool has a radius of 20 feet. A fence is going to be built so that there is a 4-foot space around the entire pool. What is the length of the fence? Sunitha solved the problem as shown. A circle with radius 20 feet. A larger circle is 4 feet larger than the smaller circle. Radius = 24 feet. Circumference = 24 pi. What was her error? She should have used 12 in the formula, not 24. She forgot to multiply the radius by 2 in the formula. She did not add the additional fence length to the pool’s radius. She should have used 4 ft in the formula.