The formula for working out the area of a circle is:
, where is the radius of the circle.
means . Only the is squared.
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:
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 .