The perimeter of a semicircle is 20 cm less than the perimeter of the circle, what is the radius of the circle?

Answer 1

C / 2 = C - 20

πd / 2 = πd - 20

πd = 2πd - 40

-πd = -40↓

πd = 40

2πr = 40

πr = 20

r = 20 / π