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On Marcus du Sautoy's puzzle based panel game, a problem is presented with four cogs. Two of which have the same number of teeth, but are connected by two with very different numbers. The question is, will one of the two outer cogs move more quickly or slowly? Once the problem is presented, it is explained that they will actually move at the same speed.
This clip is from:
First broadcast:
7 March 2005

Classroom Ideas

This problem explores multiples in the context of number of turns each different size of gear makes. It could also be used in a lesson on ratios. The markers on the gears could be used to explore loci of the white marker on each gear can be analysed over time.