What is the radius of a circle of 480 feet?
Depending on what "a circle of 480 feet" means, the radius will have different values.
If the radius is 480 feet, then that is your answer.
If the diameter is 480 feet, then its radius is 480/2 = 240 feet.
If the circumference is 480 feet, then its radius is 480/2(pi) = 240/(pi) = 76.39 feet.