Question

There are five different routes that a commuter can take from her home to the office. In how many ways can she make a round trip if she uses a different route coming than going?

Answer 1

Answer: 120 ways

Explanation:

Let's label the routes a, b, c, d, and e. The goal is to come up with as many unique permutations as possible.

1 route: a=1. one factorial (1!) =1*1=1

2 routes: ab, ba=2. 2!=1*2=2

3 routes: abc, acb, bac, bca, cab, cba=6. 3!=1*2*3=6

4 routes: 4!=1*2*3*4=24

5 routes: 5!=1*2*3*4*5=120 ways