Stage: 4 Challenge Level: 
Some useful questions:
How long will it take if Chris swims straight to the river bank?
Is the shortest distance the fastest?
What happens if Chris aims for land half way between the previous two points?
Maximise/minimise/optimise. smartphone. Mathematical modelling. Pythagoras' theorem. Population Dynamics. engineering. biology. Calculus generally. Individual. Real world.
Published January 2005.
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