Department of Mathematics
University College Dublin

UCD Openday 1999
Mathematics Problem

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UCD Openday 1999 Mathematics Problem


eleven steps with five stones

Can Sisyphus raise a rock to the very top?

A pyramid consists of 1001 steps. Initially 500 rocks are placed, one on each of the lowest 500 steps, while the remaining steps are left empty.Sisyphus and the Demon take turns, Sisyphus moving a rock up and the Demon moving a rock down.

In each move Sisyphus must choose one rock and move it to the lowest unoccupied step above itself. In each move the Demon must choose a rock immediately above an unoccupied step and move that rock down to that step. Sisyphus takes the first move but the Demon plays with skill and cunning.

Can Sisyphus raise a rock to the very top step?
If he can, explain how?
If he can not, explain why not?




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Revised 22 Mar 1999.