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!
Age 11 to 14 Challenge Level
Is it possible to rearrange the
numbers 1, 2 ...12 around a clock face in such a way that every two
numbers in adjacent positions differ by any of 3, 4 or 5 hours?
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice.