This activity is about finding the circumferences and areas of circles using a calculator.

We need to learn the two important formulae below using the radius of a circle (r)

Circumference of a circle = 2 π r

Area of a circle = π r²

Examples

Find the circumference and area of a circle of radius 6 cm.

π is usually taken to be 3.142, but your calculator should have the π button on it which will make your calculations more accurate. Once you've done the first part of the calculation, just tap in x π and then = and you should get the correct answer. Test it out with the examples below!

Answers

Circumference = 2 π r = 2 x π x 6 = 12 x π = 37.7 cm  (1 dp)

Area = π r² =  π x 6² = π x 36 = 113.1 cm²  (1 dp)

On to the questions now!