In a group of 9 boys, three are brothers. The number of ways in which the boys can sit so that three

Question

In a group of 9 boys, three are brothers. The number of ways in which the boys can sit so that three brothers are not sitting together is

Professor PC Thomas Classes · Answer

Total arrangements $9!$. Brothers together $3! 	imes 7!$. Not together $9! - 3! 	imes 7! = 332640$.