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#41 There are three prisoners
Set by Christopher Dearlove
Three mathematicians are held prisoner and made to play a game in which they each have a blob painted on their forehead in green or blue, with an independent 50 per cent chance of either colour for each prisoner. They must all simultaneously guess their own blob colour or say nothing. They lose the game if nobody guesses or if someone guesses wrong.
How can they plan to play so they guarantee a 50 per cent chance of winning?
How can they increase their chances of winning to 75 per cent?…
