# Circles

## finding the area and perimeter of circles

In your maths exam you may be asked to find the area or circumference of a circle. This is normally on your calculator paper of your maths exam. Check out the formulae page if you can't remember how to work out the area or circumference of a circle.

## Example Question

A circular pond has a radius of 8 metres.

a) Find the area of the pond.
b) Find the circumference of the pond.

## Solution

a) The area of the pond is given by the formula A = πr2. Where r is the radius of the pond.

So area of pond = π x 82 = 201.0619298 = 201 m2 (1 decimal place.)

b) The circumference of the pond is given by the formula C = πD. Where D is the diameter of the pond.
Remember: The diameter is twice the size of the radius = 8 x 2 = 16 m

So the circumference of the pond =  π x 16 = 50.26548246 = 50.3 m (1 decimal place.)

## Test Yourself!

Find the area of the circle below. Give your answer to 1 decimal place. m2 Find the circumference of the circle below. Give your answer to 1 decimal place. cm 