Area and circumference both relate to the radius and diameter of a circle. Once you know one, you can find all of the others --It just takes a little math!

### Practice Problems

A = Π (radius)² = 16Π radius² = 16 radius = 4

circumference = 2Π × radius = 2Π × 4 = 8Π

circumference = 2Π × radius = 2Π × 4 = 8Π

circumference = 2Π(radius) = 26Π 2 × radius = 26 radius = 13
area = Π(radius)² = Π(13)² = 169Π