Question

Evaluate $\frac{n!}{(n-r)!}$, when.
$n=9,r=5$.

Answer 1

Given, $n=9,r=5$

Therefore the value of $\frac{n!}{(n-r)!}=\frac{9!}{(9-5)!}=\frac{9!}{4!}=\frac{9\times 8\times 7\times 6\times 5\times 4!}{4!}$
$=9\times 8\times 7\times 6\times 5=15120$