Re: Synthetic Division?

Ian Johnston wrote:
When I run maths holidays and weekends for kids, one of the most popular bits is a session on isomorphic games - apparently very different, but in fact using exactly the same mathematical principles. 

One I like is 'number scrabble'. You and your opponent take it
in turns to choose numbers from 1 to 9---no repeats allowed.
The winner is the first whose collection of numbers contains
a set of three which add up to 15.

Or, you could play noughts and crosses on a three-by-three
magic square.

Actually, that's the only one I can think of off-hand, excluding
analysing nim using binary numbers. What others do you use?
.