Key factors
Clever logic should enable you to find the nine-figure number that I have in mind. It consists of the digits 1 to 9 in some order, and in the number each digit is next to another that differs from it by one.
In just one case a digit has both neighbours differing from it by one. Furthermore, the solution is exactly divisible by more than three-quarters of the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12.
What is the nine-figure number?
WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 9 May. The Editor’s decision is final. Please send entries to Enigma 1692, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).
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Answer to 1686 Squaring the circle: 132 slabs were used. The radius of the courtyard was 6 metres.
The winner John Woolhouse of Sheffield, South Yorkshire, UK
