Do now: Work out the circumferences and areas of these circles

10 cm

12 cm

9 cm

2 cm

1.5 cm

How well did you do?

10 cm

12 cm

9 cm

2 cm

1.5 cmC = 31.4 cm

C = 56.5 cmC = 37.7 cm

C = 9.4 cm

C = 6.3 cm

How well did you do?

12 cm

9 cm

2 cm

1.5 cmA= π × 52

A = 78.5 cm2

5 cm

A= π × 62

A = 113.0 cm2

A= π × 12

A = 3.1 cm2

A= π × 92

A = 254.3 cm2

A= π × 1.52

A = 7.1 cm2

Circumference = π × diameterC=πd

OR

Circumference = 2 × π × radiusC=2πr

Area = π × radius × radius A=πr2

Did you remember these important formulae?You are expected to remember these in your GCSE exam.

diameter

radiu

s