Answer: 220
Step-by-step 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
[tex]C(n,r)=\dfrac{n!}{r!(n-r)!}[/tex]
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 =
[tex]C(12,9)=\dfrac{12!}{9!(12-9)!}\\\\=\dfrac{12\times11\times10\times9!}{9!3!}\\\\=\dfrac{1320}{6}\\\\=220[/tex]
Hence, the number of different groups of 9 can be formed from the 12 volunteers = 220
