Question:
How many committee of five persons with a chairperson can be selected from 12 persons? [Hint: Chairman can be selected in 12 ways and remaining in 11 C4.]
Solution:
We know that,
nCr
$=\frac{n !}{r !(n-r) !}$
Number of ways a chairperson can be selected =12
Selection of 4 other people =11C4
$=\frac{11 !}{4 ! 7 !}=330$
Selection of 5 people = 330 × 12
=3960