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Just reflecting

Joe has been showing Penny a few optical experiments. In one experiment he placed six mirrors vertically to form a regular hexagon with small gaps between the mirrors. Through one gap he shone a laser beam so it emerged straight from the gap diametrically opposite.

Penny then had to work out the smallest angle through which the beam must be rotated so that it emerged from the same gap as before, after being reflected just once by all six mirrors.

What was that small angle (rounded to the nearest degree)?

WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 18 March. The Editor’s decision is final. Please send entries to Enigma 1532, ¿ìè¶ÌÊÓƵ, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).

Answer to 1526 Degrees of error: The true temperature was 80 °C

The winner Mike Waterman of Camberley, Surrey, UK