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Enigma Number 1595

All mapped out

My house appears on each of three overlapping local maps. Each map is half a metre square and all are to the same scale. To ease map handling, I have produced a composite version by pasting them on top of one another to form a single sheet which correctly aligns all the roads and other features. I have now trimmed off those parts of the map which I do not need, thereby creating a complete square composite map, almost exactly a whole number of millimetres along each side. As it happens, I could not have produced a larger square even if, instead, the maps had been entirely blank sheets of paper. To the nearest millimetre, what is the length of the side of the composite map?

WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 16 June. The Editor’s decision is final. Please send entries to Enigma 1595, ¿ìè¶ÌÊÓÆµ, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).

Answer to 1589 Coin-cidence: 13 coins

The winner Philip Epstein of Fulshear, Texas, US