Here is a problem that at first sight looks as if it needs some advanced mathematics involving calculus to be applied to get a solution. In fact it has a very simple solution that is guaranteed to elicit a groan from any mathematician that doesn't spot it!

Two footballers are running towards each other, each travelling at constant speed of 5 metres a second. When they are 200 metres apart a fly that has been sitting on one of the players sets off towards the other player at a speed of 10 metres a second. When the fly reaches the other player it immediately reverses direction and sets off back towards the first player. This continues until the two players collide. How far did the fly travel?

The two players are approaching each other with a relative speed of 10 metres a second. So they take 20 seconds to cover the 200 metres before they collide. The fly is always travelling at 10 metres a second, so it must travel 200 metres in the 20 seconds.

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