# Geometry

Remember:

$Radius = \frac{1}{2}diameter$

$Diameter = 2 \times radius$

## Circumference of a circle

For any circle with a diameter, d, the circumference, C, is found by using the :

$C = \pi d$

where $$\pi = 3.14$$

Question

Calculate the circumference of the circle shown below.

$C = \pi d$

$= 3.14 \times 20$

$= 62.8cm$

Question

Calculate the circumference of the circle shown below.

As you can see from the diagram, the radius is 12 cm.

Remember $$Diameter = 2 \times radius$$

$Diameter = 2 \times 12 = 24cm$

$C = \pi d$

$= 3.14 \times 24$

$= 75.36cm$