#### Answer

504

#### Work Step by Step

The number of permutations of n items, where p items are identical, q items are
identical, r items are identical, and so on, is given by
$\frac{n!}{p!q!r!...}$
The number of different signals consisting of nine flags that can be made using three white flags, five red flags, and one blue flag is:
$\frac{9!}{3!5!1!}$ = 504 ways