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Marcus du Sautoy presents a problem about his imagined commute to work. He can travel 10mph on the way there, and 15mph on the way back. The distance is fixed, so the question is, what is his average speed over the whole journey? Panellists on his puzzle game work towards the solution - which is not simply the mean of the two numbers. Du Sautoy presents the solution, using speed = distance / time.
This clip is from:
First broadcast:
14 February 2005

Classroom Ideas

This could be used as a challenge question or plenary after a series of lessons on speed/time graphs. It could also be used as a good extension for those looking beyond the simple mean towards 'weighted means' at Statistics GCSE, for example.

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