Circles Mixed Exercises

area, circumference, diameter and radius

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

Problem 1

If a circle's diameter is 10, calculate its circumference and area?

circumference = Π×diameter = 10 Π
radius = ÷2 = 10 ÷ 2 =5
area = Π(radius)² = Π(5)² = 25Π
Problem 2

A circle's area is 16Π. What is its circumference?

A = Π (radius)² = 16Π radius² = 16 radius = 4
circumference = 2Π × radius = 2Π × 4 = 8Π
Problem 3

If a circle has a circumference of 26Π, what is its area

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