An overnight express company must include seven cities on it

An overnight express company must include seven cities on its route. How many different routes are possible, assuming that it matters in which order the cities are included in the routing?

Solution

First stop: 7 cities possible
Second stop: 6 cities possible
Third stop: 5 cities possible
etc....

The answer is 7! or 7x6x5x4x3x2x1 which equals 5,040.