Question: Say, there is n number of twins. How many ways can they be seated at a round table if k pair of twins has to sit together?
Solution: I solved it in the following way. Is it correct?
If I subtract k pairs from 2n, total no. of people= 2n-k. This (2n-k) can be arranged in (2n-k-1)! ways.
Again k no. of pairs can be arranged in 2^k ways among themselves. So, total no. of ways= (2n-k-1)! * 2^k