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Question

Mathematics Question on Permutations

The number of ways in which 55 ladies and 77 gentlemen can be seated in a round table so that no two ladies sit together, is

A

72(720)2\frac{7}{2}{{(720)}^{2}}

B

7(360)27{{(360)}^{2}}

C

7(720)27{{(720)}^{2}}

D

720720

Answer

72(720)2\frac{7}{2}{{(720)}^{2}}

Explanation

Solution

First we fix the alternate position of 7 gentlemen in a round table by 6! ways. There are seven positions between the gentlemen in which 5 ladies can be seated in 7P5^{7}{{P}_{5}} ways.
\therefore Required number of ways
=6!×7!2!=6!\times \frac{7!}{2!}
=72(720)2=\frac{7}{2}{{(720)}^{2}}