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Q2

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john_haddock
 Post subject: Q2
 Post Posted: Wed May 27, 2009 10:36 pm 
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Course Students


Posts: 6
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 randomly, what is the probability that only 1 letter will be put in the envelope with the correct address?

1/24
1/8
1/4
1/3
3/8
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stock.mojo11
 Post subject: Re: Q2
 Post Posted: Thu May 28, 2009 12:11 am 
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Forum Guests


Posts: 42
john_haddock wrote:
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 randomly, what is the probability that only 1 letter will be put in the envelope with the correct address?

1/24
1/8
1/4
1/3
3/8



Was discussed here in length post5773.html

total number of ways of arranging 4 letters in 4 envelopes = 4 X 3 X 2 X 1 (denominator)

One letter in correct env Can be any of the 4 right. so 4 ways

Now 3 letters and 3 env. all should go into wrong env

in first env you can pu one of the two wrong letters. then left with 2 letters and 2 envelopes. you can put those in 1 way. Hence it is 4 X2 X1 X 1

Ans 8/24 =1/3
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StaceyKoprince
 Post subject: Re: Q2
 Post Posted: Mon Jun 01, 2009 5:46 pm 
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ManhattanGMAT Staff


Posts: 6077
Location: San Francisco
Thanks, stock, for the link to the prior discussion. Just a reminder to everyone: search first to see whether a problem has already been discussed. Then you don't have to wait for a reply! :)

john, follow that link and let us know if that doesn't answer your question.

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Stacey Koprince
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ManhattanGMAT
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