Answer
$1680$
Work Step by Step
Use the formula $P(n,r)=\dfrac{n!}{(n-r)!}$.
Here we have $n=8$ and $r=4$:
Substitute these values into the formula above to obtain:
$P(8,4)=\dfrac{8!}{(4)!}\\$
$P(8,4)=\dfrac{8!}{4!}\\$
$P(8,4)=\dfrac{8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1}{4\cdot3\cdot2\cdot1}$
Cancel out the common factors to obtain:
$P(8, 4) = 8\cdot7\cdot6\cdot5\\
P(8, 4) =1680$
