Coin Cogs

Age 7 to 11 Challenge Level:

Coin Cogs

Here is a picture of a UK £2 coin with two pink circles drawn on it:

two pound coin

If you look at the band between the two pink circles, you will see that it contains lots of cogwheels.

Can you explain what is wrong with these cogs?

To get an idea of how cogwheels move, you could look at the interactivity in this month's Turning Cogs problem.

This problem has deliberately been left open-ended, but if children have explored the interactivity in the Turning Cogs problem, then they will become familiar with the way that cogs work. Allowing them to experiment and talk about their discoveries with each other might be the best way to get them going on this challenge.

If the interactivity is not available,you may like to print off this sheet of cogs to cut out and give to the children, or use on an OHP.