Question

In how many ways can 4 different contracts be distributed among 12 different firms, if no two contracts are awarded to the same firm?

Answer 1

The first contract can go to any of 12 firms. The second can go to any of the remaining 11 firms, and so on. Finally, the 4th contract can go to any of the 9 firms that don't yet have a contract.

The number of ways the contracts can be awarded is

... 12×11×10×9 = 11,880