The Careless Mailing ClerkAfter a typist has written ten letters and had addressed the ten corresponding envelopes, a careless mailing clerk inserted the letters in the envelopes at random, one letter per envelope. What is the probability that exactly nine letters were inserted in the proper envelopes?  |Contact| |Front page| |Contents| |Store| |Up| Copyright © 1996-2012 Alexander Bogomolny If nine letters are in the correct envelopes, the tenth must be also, so the probability is zero. References
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