A town orchestra needs 3 new flute players and 4 new trumpet players. 8 flutists and 11 trumpeters try out, then the orchestra should select 3 flutists from 8 and 4 trumpeters form 11.
They can choose 3 flutists from 8 in
[tex] C_8^3=\dfrac{8!}{3!(8-3)!}=\dfrac{8!}{3!\cdot 5!}=\dfrac{1\cdot 2\cdot 3\cdot 4\cdot 5\cdot 6\cdot 7\cdot 8}{1\cdot 2\cdot 3\cdot 1\cdot 2\cdot 3\cdot 4\cdot 5} =56 [/tex] ways.
They can choose 4 flutists from 11 in
[tex] C_{11}^4=\dfrac{11!}{4!(11-4)!}=\dfrac{11!}{4!\cdot 7!}=\dfrac{1\cdot 2\cdot 3\cdot 4\cdot 5\cdot 6\cdot 7\cdot 8\cdot 9\cdot 10\cdot 11}{1\cdot 2\cdot 3\cdot 4\cdot 1\cdot 2\cdot 3\cdot 4\cdot 5\cdot 6\cdot 7} =330 [/tex] ways.
Use the product rule: 56·330=18480 ways for conductor to choose his new members.
