The multiplication rule of counting indicates that the product of the outcomes of each event gives the total number of possible outcomes for the series of all 5 events. There are 5 outcomes for the first city, 4 outcomes for second city, 3 outcomes for the third city, 2 outcomes for the fourth city, and 1 outcome for the final city. Write the product of the outcomes.
(first city) · (second city) · (third city) · (fourth city) · (final city)

= 5 · 4 · 3 · 2

Note that factorial notation can be used here, since we have the product of consecutive decreasing counting numbers.

Recall that
n! = n(n − 1)(n − 2) 1.

Here,
n = 5
and
5! = 5 · 4 · 3 · 2

Step 3
Multiply to find the total number of possible outcomes.
5! = 5 · 4 · 3 · 2 · 1

= ?

So by the multiplication rule of counting, the sales representative has different choices for the order in which to visit the cities.