Question

A man has 9 friends, 4 boys and 5 girls. In how many ways can be invite them, if there have to be exactly three girls in the invites?

• A. $320$
• B. $160$
• C. $80$
• D. $200$

Answer 1

Answer: (B)

$160$

He can select three girls in ${}^5{C}_3$ ways = 10 ways
He can select boys in ${[}^4{C}_0{+}^4{C}_1{+}^4{C}_2{+}^4{C}_3{+}^4{C}_4]$ ways = 16 ways
Total number of ways $=10\times 16$ $=160$