Sometimes the product rule counts some outcomes multiple times. When this happens, you need to correct for overcounting by dividing.
For example, if you want to count 2-person committees from 5 people, multiplying 5×4=20 overcounts because picking Alice then Bob is the same committee as picking Bob then Alice.
Divide by 2!=2 to get the correct answer: 20/2=10 committees. This pattern leads to combinations, which you will learn in a later section.