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Ad hoctagon

I HAVE eight rods. I can use three of them to make the sides of a right-angled triangle of area 10 square centimetres.

Alternatively, I can use all eight of them to make the sides of an octagon, all of whose angles are the same, and all of whose vertices lie on a circle.

What is the area of that octagon?

£15 will be awarded to the sender of the first correct answer opened on Wednesday 18 February. The Editor’s decision is final. Please send entries to Enigma 1528, ¿ìè¶ÌÊÓƵ, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address). The winner of Enigma 1522 is Richard Kennaway of Norwich, UK.

Answer to 1522 Real in the lead

Twente beat Sporting; Sporting has a final total of 9 points and Twente has a total of 5 points

Visit www.newscientist.com/topic/enigma for recent puzzles and worked solutions