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Current Student
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how many different ways to seat 6 people around a circular [#permalink]
 01 Aug 2008, 13:56
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how many different ways to seat 6 people around a circular table if 2 of the 6 refuse to sit adjacent to one another?
96?
hmm agree 72
Last edited by young_gun on 01 Aug 2008, 16:11, edited 1 time in total.
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Intern
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my guess 72
total ways = 5! = 120
pair together = 2*4! = 48
answer = 120-48 = 72
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Manager
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I think it's 72
6 people can seated in 5! ways around a round table.
if 2 cant sit in ajacent seats- one of then has only 3c1 seats and te rest have 4! wayr to be seated.
we are left with 3*4!= 72 ways
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Manager
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why does the permutation of n objects become (n-1)! in a circle?
_________________
kris
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Manager
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It is because if you take for example 3 elements in circle called A, B and C then there possible arrangements in circle are
only 2 instead of 6.
ABC
CAB
BCA
These three arrangements in circle are same....if you arrage them in circle then you will realize how it is.
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Manager
Joined: 07 Jul 2007
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It is because if you take for example 3 elements in circle called A, B and C then there possible arrangements in circle are
only 2 instead of 6.
ABC
CAB
BCA
These three arrangements in circle are same....if you arrage them in circle then you will realize how it is.
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