Can you solve it? Maths on the back of an envelope
by Alex Bellos from on (#4QZ5K)
Stationery puzzles to get your brain moving
UPDATE: Solutions now up and the winners of the mnemonic challenge announced
Today, we're pushing the envelope.
1) A piece of paper is folded to make a shape that looks a bit like the back of an envelope, illustrated below. If the paper is unfolded again to make a flat sheet, what shape will it be? Prove it.
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