Open the box
I started with a rectangular piece of card a whole number of centimetres long by a whole number of centimetres wide, one of those numbers being a prime. Then I cut out an identical small square from each corner of the card and discarded the four squares. I folded up the four “flaps” on the remaining piece of card to form an open-topped box, choosing the size of the cut squares so that the volume of this open box was the biggest possible. Having made the box, I found that the length of its rectangular base was four times its width.
What were the dimensions of the original piece of card?
WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 17 October. The Editor’s decision is final. Please send entries to Enigma 1715, Â鶹´«Ã½, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).
Answer to 1709 Not original: The alley is 189 centimetres wide
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The winner Richard Brookfield of Worcester, UK
