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Arrangements at a round table question

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Arrangements at a round table question

by houstonrockets16 » Mon Aug 16, 2010 11:15 am
At a dinner party, 5 people are to be seated around a circular table. Two seating arrangements are considered different only when the positions of the people are different relative to each other. What is the total number of different possible seatnig arrangements for the group?

a) 5 b) 10 c) 24 d) 32 e) 120

Please help! =) I am really struggling to come up with this answer..
thank you guys

CORRECT ANSWER: [spoiler]C) 24[/spoiler]
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by Prashantbhardwaj » Mon Aug 16, 2010 11:20 am
Its a simple circular permutation question.

where total no of permutations is = nPr/r


5P5 / 5 = 5! / 5 = 24 Ans.
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by Gurpinder » Mon Aug 16, 2010 11:24 am
houstonrockets16 wrote:At a dinner party, 5 people are to be seated around a circular table. Two seating arrangements are considered different only when the positions of the people are different relative to each other. What is the total number of different possible seatnig arrangements for the group?

a) 5 b) 10 c) 24 d) 32 e) 120

Please help! =) I am really struggling to come up with this answer..
thank you guys

CORRECT ANSWER: [spoiler]C) 24[/spoiler]
Anytime you have a circular permutation problem remember this: (the total # - 1 ) factorial

So the total number of people here is 5. Therefore (5-1)! = 24.
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by madhukumar_v » Mon Aug 16, 2010 11:53 am
Two formulae for circular permutation.

1. (n-1)!

2. (n-1)!/2 (If you want to consider people sitting on the opposite ends when flipped to be the same)
Example: for 4 people, 1-2-3-4

1 1
3 2 = 2 3
4 4
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by srajan » Mon Aug 16, 2010 4:37 pm
I would like to point out that if you had another condition that the chair is also important then the answer was 120.

Consider that there are 5 chairs and seating on a different chair makes a different arrangement then you would have 5P5.
i.e. 5! = 120
But since nothing sort of that is mentioned 5P5/5=24 is the correct answer.
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