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Four vehicles travelled on a road. What can you deduce from the times that they met?

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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?

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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?

# One and Three

##### Stage: 4 Challenge Level:

This problem stimulates students into creating some kind of diagram as an aid to visualisation. Hopefully the phrase "ratio of the speeds" will encourage students to think through how the simulation is not significantly altered if the speeds of both boats were, for example, doubled or halved. This is a useful problem for connecting speed, distance and time, and may also offer students a useful context in which to use algebra to express relationships containing known and unknown quantities.