Circumference = 2 × pi × radius C = 15 15 = 2 × pi × r 15÷2 = pi × r 7.5 = pi × r 7.5÷pi = r
Radius equals to 7.5 divided by pi. You can also use this formula for circumference --> C = d × pi where d is the diameter. Then you'll have to divide your answer by 2, to get the radius. Hope i helped :)
