Answer: [tex]\frac{n!}{(n-r)!}[/tex]
Step-by-step explanation:
The number of permutations of n things taken r at a time is given by the following formula:
[tex]^nP_r=\frac{n!}{(n-r)!}[/tex]
Therefore, the formula for the number of permutations of n things taken r at a time is [tex]\frac{n!}{(n-r)!}[/tex]