How many different four-song orderings can Rob create?

Rob has six songs on his portable music player.

How many different four-song orderings can Rob create?
A . 30
B . 60
C . 120
D . 360
E . 720

Answer: D

Explanation:

The order of the four songs is important. The orderings A, B, C, D and A, C, B, D contain the same four songs, but in different orders. Both orderings must be counted. The number of six-choose-four orderings is equal to 6 × 5 × 4 × 3 = 360.