Q4 of 140 Page 317

In how many ways can 8 persons be seated at a round table so that all shall not have the same neighbours in any two arrangement?

By using the formula (n-1)! (mention in Solution-1)

So 8 persons can be arranged by 7!


Now each person have the same neighbours in the clockwise and anticlockwise arrangement


Total number of arrangement are (7!)/2 = 2520


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