Answer
The number of permutations possible
if $r$ items are taken from $n$ items.
Work Step by Step
A permutation from a group of items occurs when
no item is used more than once and
the order of arrangement makes a difference.
The number of permutations possible
if $r$ items are taken from $n$ items is
${}_{n}P_{r}=\displaystyle \frac{n!}{(n-r)!}$.