Question

A blood bank needs 9 people to help with a blood drive. 12 people have volunteered. Find how many different groups of 9 can be formed from the 12 volunteers.

Answer 1

Answer: 220

Explanation:

The number of ways to choose r people out of n is given by Combination ( where order does not matter) and the formula to find them is

`C(n,r)=(n!)/(r!(n-r)!)`

Now , it is given that

A blood bank needs 9 people to help with a blood drive. 12 people have volunteered.

Then, the number of different groups of 9 can be formed from the 12 volunteers =

`C(12,9)=(12!)/(9!(12-9)!)\\\\=(12*11*10*9!)/(9!3!)\\\\=(1320)/(6)\\\\=220`

Hence, the number of different groups of 9 can be formed from the 12 volunteers = 220