The formula for working out the **area** of a circle is:

, where is the radius of the circle.

means . Only the is squared.

- Question
Find the area of the following circles, using .

a) a circle of radius

b) a circle of diameter

a) , so we calculate:

b) The diameter is , so the radius is . We calculate:

- Question
The dartboard above has a radius of . The bullseye in the centre of the board has a radius of .

By calculating the area of the two circles, work out the area of the dartboard outside of the bullseye, using .

Remember, the area of the large circle is .

The area of the small circle is .

So, the area of the dartboard outside of the bullseye is .

When calculating the area of a circle, remember to use the radius, not the diameter.