  # Find Circumferences of Circles Using Their Radii (1)

In this worksheet, students use formulae to calculate the circumferences of circles given their radii. Key stage:  KS 3

Curriculum topic:   Geometry and Measures

Curriculum subtopic:   Solve Problems Involving Perimeters and Areas of 2D Shapes

Difficulty level:   #### Worksheet Overview

This worksheet is about finding the circumferences of circles.

The circumference of a circle is its perimeter or the distance around its edge.

You must learn these two important formulae for a circle of radius, r or diameter, d:

Circumference of a circle = 2πr

Circumference of a circle = πd  Example 1

Find the circumference of a circle of radius 6 cm.

Circumference = 2 × π × r = 2 × π × 6 = 12 × π = 37.7 cm  (1 decimal place)

Example 2

Find the circumference of a circle of diameter 6 cm.

Circumference = π × d = π × 6 = 18.8 cm  (1 decimal place)

Use a scientific calculator to work out your answer.  If you don't have one in the house, you can access one online.

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