Question
The number of ways in which 20 volunteers can be divided into groups of 4, 7 and 9 persons is-
- 16C7× 13C2
- 20C7 × 11C4
- 20C4 × 16C7
- 20C9 × 13C9
Hint:
Since we have to make groups of 4, 7 , 9 people out of 20 volunteers , find out the number of people that can be selected and similarly those who are selected in one group , they will not participate in other groups.
The correct answer is: 20C4 × 16C7
We have to make groups of 4, 7 , 9 people out of 20 volunteers
4 people out of 20 can be selected in 
7 people out of remaining 16 can be selected in 
9 people out of remaining 9 can be selected in 
Thus, the number of ways in which 20 volunteers can be divided into groups of 4, 7 and 9 persons is
.
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