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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 = diameter ÷ 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 direction arrow radius² = 16 direction arrow 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 direction arrow 2 × radius = 26 direction arrow radius = 13

Area = Π(radius)² = Π(13)² = 169Π

Interesting Fact about Circumference and Area

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