Math
posted by Tracy on .
Tom's new CD player has a 9disc changer. If she owns 45 CDs, in how many ways can he choose 9 CDs to listen to?
After picking 9 CDs, in how many ways can he order them in the 9 slots of the changer?

45 items, taken 9 at a time
C(45,9)=45!/9!(459)!
orders: 9!