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In how many ways can friends sit at a dinner table if two of them, Anna and Bob, insist on having exactly two people seated between them? (As usual, two seatings are considered the same if one is a rotation of the other.)

 Jun 13, 2017
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Assuming that there are  "n"  total  people

 

Anchor Anna and Bob in any two chairs separated by two people.....then the other people can be arranged in (n - 2)! ways

 

And Anna and Bob  themselves can be arranged in 2 ways

 

So.....the total number of arrangements  =   2 * ( n - 2)!   ways

 

 

cool cool cool

 Jun 13, 2017
edited by CPhill  Jun 13, 2017
edited by CPhill  Jun 13, 2017
edited by CPhill  Jun 13, 2017

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