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Equal Colours

Problem

A box contains a mixture of black and white discs, with more black than white discs. A game is played by taking one disc at a time, at random, and without replacement. If an equal number of each colour have been removed the game stops and the player wins.

It is found that the player has an equal chance of winning or losing.

If the box contains twelve discs in total, find the number of black discs.

Problem ID: 193 (11 Dec 2004)     Difficulty: 3 Star

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