A coin is a circle. Circumference of a circle is determined using this following formula 2 × π × r = c with r as the radius, and c as the circumference
Find the radius To find the radius, use the formula above 2 × π × r = c 2 × π × r = 18π 2π × r = 18π r = 18π/2π r = 9 The radius of the circle is 9 cm
Find the diameter The diameter is twice as long as the radius. d = 2 × r d = 2 × 9 d = 18 The diameter is 18 cm
