SOLUTION: A secretary types letters to 4 people and addresses four envelopes. If she inserts the letters at random each in a different then what is the probability that exactly 3 letters wil

Algebra ->  Probability-and-statistics -> SOLUTION: A secretary types letters to 4 people and addresses four envelopes. If she inserts the letters at random each in a different then what is the probability that exactly 3 letters wil      Log On


   



Question 388801: A secretary types letters to 4 people and addresses four envelopes. If she inserts the letters at random each in a different then what is the probability that exactly 3 letters will go in to the correct envelopes
Answer by robertb(5830) About Me  (Show Source):
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If 3 letters go in to the correct envelopes then ALL 4 letters would have been inserted in the correct envelopes, which is 1 chance in 4! = 24 ways. Therefore the probability is 1/24.