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Tanya prepared 4 different letters to be sent to 4 different [#permalink]
10 Dec 2006, 07:28

Tanya prepared 4 different letters to be sent to 4 different addresses. For each letter, she prepared an envelope with its correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that exactly 2 letters will be put into 2 envelopes with its correct address? _________________

Chance of 1st letter being correct = 1/4
Chance of 2nd letter being correct = 1/3
Chance of 3rd letter being incorrect = 1/2
Chance of 4th letter being incorrect =1

There is no OA cos adaptation of GMAT prep question that asks same thing but for 1 letter in correct position. I've drawn a table of all posibilities - correct answer is 1/4

I've labelled envelopes, 1,2,3,4 with correct letter being A=1, B=2, C=3, D=4