Diagonal diversion
A niece, Amy, asks me to help her revise some arithmetic, her favourite subject, so we make 25 cards numbered consecutively from 1 to 25, which we shuffle and deal out in a 5-by-5 grid. She then multiplies together the numbers in each row and writes the product at the end of the row; we call these products A to E, top to bottom. Amy then repeats the process for the columns, and these are the products F to J, left to right. Having got all these correct, she decides to find the product for the leading diagonal (top left to bottom right), and she calls this K.
Given that A = 483840, B = 604032, C = 90440, D = 57960, F = 193375, G = 1530144, H = 288000, I = 258552, what value should Amy obtain for K?
WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 19 January 2011. The Editor’s decision is final. Please send entries to Enigma 1625, Â鶹´«Ã½, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).
Answer to 1619 Stack of marbles: the rectangle is 7 × 23
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The winner David Croome of Par, Cornwall, UK
