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Chris and Jo decide to play a game.

They put some red and some blue ribbons in a box.

They each pick a ribbon from the box without looking (and without replacing them).

Jo wins if the two ribbons are the same colour and Chris wins if the two ribbons are a different colour.


How many ribbons of each colour would you need in the box to make it a fair game?

Is there more than one way to make a fair game?


This problem is based on one offered by Doug Williams at the 2003 ATM conference in Bath UK. See also

Click here for a poster of this problem.