How many ways can 4 DVDs be arranged on a shelf?
Solution:
There are 4 ways to choose the first DVD, 3 ways to choose the second, 2 ways to choose the third and 1 way to choose the last. In other words, there are 4 x 3 x 2 x 1 = 4! =24 ways to arrange the DVDs.
Example: How many ways can John, Katherine, Luke, Melanie and Nick sit at a table?
Solution: The number of ways to arrange these five people is 5!
5! = 5 x 4 x 3 x 2 x 1 = 120. There are 120 permutations.
Example: How many ways can n objects be arranged?
Solution: n objects can be arranged in n! ways.