So use half the surface area formula: SA=2πr^2 and plug in what you already know since you don't know the radius yet, solve for it using the circumference C=2πr 514.96=3.14(2)r 82=r
SA=2π(82)^2 SA=6.28(6724) SA=42,226.72 so your answer is 42,226.72 yards squared
