Question

A round table conference is to be held between 20 delegates of 2 countries. In howmany ways can they be seated if two particular delegates are or never to sit together.?

• A. (19) ! - 2 (19)
• B. (19) ! +2 (19)
• C. (19) ! - 3 (19)
• D. (20) ! - 2 (19)

Answer 1

The correct option is A (19) ! - 2 (19)

Number of ways in which 20 delegates can be arranged $=(20-1)!=19!$

Now we have to make sure 2 particular delegates never sit together, So number of ways in which they are together $=2\ast 19$

So, Answer will be $19!-2\ast 19$