## Thinking Mathematically (6th Edition)

The number of possible permutations if r items are taken from n items is nPr =$\frac{n!}{(n-r)!}$ The number of ways that the four remaining jokes can be ranked is: = 4P4 =$\frac{4!}{(4-4)!}$ =$\frac{4!}{0!}$ =24 ways