Enigma 1684: In the fold
8 February 2012
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From New Scientist #2851, 11th February 2011 [link]
I have taken a square piece of paper with an area equal to a two-figure number of square centimetres.
The corners are labelled A, B, C and D clockwise around the square. I have folded the square with one straight fold so that the corner A lies midway between C and D. I have then opened up the sheet and measured the length of the fold line. It is an even number of centimetres.
How long is it?