11 persons are sitting ina row. how many ways can 11persons be arranged in a row such that 3 persons should always be together?  Choose the correct choice from the following answers:
A) 7!×3! B) 7!×2! C) 9!×3! D) 7!×1! E) 6!×2!
Given that three particular persons should always be together. Hence, just group these three persons together and consider as a single person.   Therefore we can take total number of persons as 9. These 9 persons can be arranged in 9! ways.   We had grouped three persons together. These three persons can be arranged among themselves in 3! ways.   Hence, required number of ways   =9!×3!   9!×3!
<result>C</result>
11 persons are sitting ina row. how many ways can 11persons be arranged in a row such that 3 persons should always be together?