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Gus is older than Flora.
Alessandro is older than Zara but younger than Flora.
Oliver is younger than Gus but older than Zara.
Yvette is younger than Gus.
Alessandro is older than Oliver.
Flora is younger than Yvette.
Can you list these six friends in order of age?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?