1. When fitting a cycle computer, you have to type in the wheel circumference. This helps the computer to work out how far you have travelled.
What this video clip to see how one man measures the circumference of his bikes

2. This applet shows why his method measures the circumference
Click on the circle to go to link

3. You know another way to work out the circumference of a circle.
What could you do?

4. This wheel rim has a diameter of 62cm
The tyre has a diameter of 5cm
How could you find the circumference of this wheel?
Work in your pairs
5cm
62cm

5. This wheel rim has a diameter of 62cm
The tyre has a diameter of 5cm
Show me your working out…
5cm
62cm

6. This wheel rim has a diameter of 62cm
The tyre has a diameter of 4.5 cm
The man in the video talked about different types of tyres.
How would you alter your calculation if the tyre had a diameter of 4.5cm?
4.5 cm
62cm

7. Watch the working out in this video.
What are the measurements of his wheel?
How do you know?
? cm
? cm

8. Can you write a formula for any measurements
a and b?
Show me your working out…
a cm
b cm

9. The Penny Farthing
The front wheel of this penny farthing is 55 inches in diameter, and the back is 14 inches.
How tall is the front wheel?
The worksheet asks questions about how far the circumferences of the two wheels.