Enigma 1551: The same chance
13 March 2012
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From New Scientist #2714, 27th June 2009 [link]
Harry and Tom each had a set of 15 red and six coloured snooker balls. Each of them had a bag, into which he put one or more of the red balls and four or more of the coloured balls from his set. Although Tom put more balls into his bag than Harry put into his bag, each of them calculated that if he picked four balls out of his bag simultaneously at random there was a 1 in X chance that all four would be coloured.
X represents the same number for each of them.