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Puzzle for Today

Puzzle No. 354 – Monday 12 November

Seven people sit round a circular table at a Chinese restaurant and each orders a different dish. Unfortunately it’s the waiter’s first day on the job and he places the wrong dish in front of each of the seven diners. As this is a Chinese restaurant the table can be rotated. Is it possible to do this so that at least two diners get the dish they ordered?

Today’s #PuzzleForToday has been set by Dr Lynda White, Department of Mathematics, Imperial College London

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There are 7 possible rotations of the table including the initial one in which no-one has their own dish. By rotating the table each of the 7 diners has their own dish in at least one of the other 6 rotations. Since 7 is greater than 6 there is at least one rotation with 2 (or more) diners getting their own dishes.

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