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At first glance it may seem surprising that the two given distances fix the length of the pool. This context will also stimulate visualisation, as students 'picture' the motion of each swimmer and then watch for the moments when they cross.
Why wasn't the second crossing in the same place as the first?
If the swimmers can keep this going indefinitely will they have eventually had a crossing point everywhere along the length of the pool?
What happens if they both swim twice as fast?
What would happen if the pool was twice as long?
Brian swims at twice the speed that a river is flowing, downstream from one moored boat to another and back again, taking 12 minutes altogether. How long would it have taken him in still water?
At Holborn underground station there is a very long escalator. Two people are in a hurry and so climb the escalator as it is moving upwards, thus adding their speed to that of the moving steps. ... How many steps are there on the escalator?