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sgrover
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13 persons take their places at a round table. What is teh 23 Jun 2006, 16:47
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13 persons take their places at a round table. What is teh probability that 2 particular persons do not sit together?



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quangviet512
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13 persons take their places at a round table. What is teh 23 Jun 2006, 21:00
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I think the prob is 10/12=83.33%
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helg
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13 persons take their places at a round table. What is teh 23 Jun 2006, 23:03
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I think its 1-(11!/13!)=1-(2/12)=5/6
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Professor
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13 persons take their places at a round table. What is teh 23 Jun 2006, 23:23
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= 1 - 2(11!) / 12!
= 5/6


helg
I think its 1 - (11!/13!) = 1 - (2/12) = 5/6
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how "11!/13! = 2/12 ?"
11!/13! = 1/(12x13)
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quangviet512
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13 persons take their places at a round table. What is teh 24 Jun 2006, 03:20
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it is much easier way to find the answer
if we have A,B and A has got a place. So we only have 10 choices for B in the left 12 places.
It means that the prob is 10/12=5/6
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13 persons take their places at a round table. What is teh 24 Jun 2006, 09:30
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quangviet512
it is much easier way to find the answer
if we have A,B and A has got a place. So we only have 10 choices for B in the left 12 places.
It means that the prob is 10/12=5/6
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beautiful :!:

Got the same answer, but used the factorial method...
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13 persons take their places at a round table. What is teh 24 Jun 2006, 10:14
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quangviet512 says

Quote:
it is much easier way to find the answer
if we have A,B and A has got a place. So we only have 10 choices for B in the left 12 places.
It means that the prob is 10/12=5/6
Show more


Out of 13 places if A takes first place then there should 11 places available for B. so prob should be 11/12

I think I am missing something.

quangviet512 Can you explain it further !!

Thanks in advance
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13 persons take their places at a round table. What is teh 24 Jun 2006, 10:20
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Nope. B has 10 places only. Out of 13, one place is taken by A, and B can't sit either to the left, or to the right of A. Hence 10.
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13 persons take their places at a round table. What is teh 25 Jun 2006, 01:26
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Professor
= 1 - 2(11!) / 12!
= 5/6


helg
I think its 1 - (11!/13!) = 1 - (2/12) = 5/6

how "11!/13! = 2/12 ?"
11!/13! = 1/(12x13)
Show more


yep, you are right.
don't know how I could get this result :(



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