Question

Four students of class X, five students of class XI and six students of class XII sit in a row. The number of ways, they can sit in a row so that students belonging to the same class are together is :

• A. 3! 4! 5! 6!
• B. 3 $\times$ 4! 5! 6!
• C. 4! 5! 6!
• D. $\frac{15!}{4! 5! 6!}$

Answer 1

Answer: (A)

3! 4! 5! 6!

Answer 2

Treating them as three groups, the three groups can be arranged in 3! ways. There after each group can be arranged internally. Total number = 3! $\times$ 4! $\times$ 5! $\times$ 6!