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## 'Odd Stones' printed from http://nrich.maths.org/

This could be a useful extension activity helping students to
break away from too readily expecting odd
or even to be the important characteristic. Odd or even-ness can be
seen more generally as the remainder after a division by two, and
this problem depends on remainders using a different
divisor.

This context has more possibilities than the simple question posed
in the problem. It is capable of building up into a rich dynamical
system well within the scope of a Stage 4 student. The number of
stones and more especially the number of circles are the key
variables.