Find the number of ways of seating 5 Indians, 4 Americans and 3 Russians at a round table so that
presons of same nationality sit together.

Explanation

Treat the 5 Indians as one unit, the 4 Americans as the second unit and the 3 Russians as the third unit. These 3 units can be arranged at round table in (3-1)!=2! Ways.
Now, the 5 Indians among themselves can be permuted in 5! Ways. Similarly, the 4 Americans in 4! ways and the 3 Russians in 3! ways. Hence the number of required arrangements is `2! xx 5! xx4! xx3!`