99 Percentile Qs Bank for JEE MainMathematicsPermutation and Combination
The number of ways in which n boys and n girls can be arranged in a row such that all the boys are together and all the girls are also together is equal to
Options
- Athe number of ways in which n boys and n girls can be arranged in a row
- Bthe number of ways in which n boys and n girls can be arranged in a row such that all the girls are together
- Cthe number of ways in which n boys and n girls can be arranged in a row such that no two girls are together
- Dnone of these
Correct answer
D. none of these
Step-by-step solution
Making 2 groups of n girls and n boys and arrange them =n ! n ! 2 ! Now number of ways to arrange n boys and n girls no two girl or boy are together. Arrange n boys alternately in n ! ways there will be (n+1) gaps, select n gaps in them and arrange girls by ^ n+1 P_n n ! ways =(n+1) ! n !