jonnysunn Posted July 3, 2007 Share Posted July 3, 2007 Tanya prepared four different letters to be sent to four different addresses. For each letter, she prepared an envelope with its correct address. If the 4 letters are to be put into the envelopes at random, what is the probability that only one letter will be put into the envelope with its correct address? OA1/3 Quote Link to comment Share on other sites More sharing options...
mfeaspire Posted July 4, 2007 Share Posted July 4, 2007 This is a variant of a more general classic problem stated below How many ways can n letters be arranged in n envelopes so that NOT a single letter is put into its rightful envelope? For an excellent inductive solution to this,with use of recurrence relations, check out http://www.physics.harvard.edu/academics/undergrad/probweek/sol16.pdf Quote Link to comment Share on other sites More sharing options...
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