what is the circumference and area of the circle if its diameter is 20 cm?

c=62.83cm

Circumference  =  2 * pi * (d/2)   =   2 * pi * (20/2)   ≈   62.83 cm

Area =  pi * (d/2)^2   =  pi * (20/2)^2   ≈  314.16 cm ^2