### Home > CCG > Chapter 10 > Lesson 10.3.4 > Problem 10-158

10-158.

Here is another way to think about the question: *“What is ?”*

How many ways are there to choose all five items from a group of five items? What happens when you substitute into the factorial formula to compute

? Since you know (logically) what the result has to be, use this to explain what must be equal to.On the other hand, how many ways are there to choose

*nothing*from a group of five items? And what happens when you try to use the factorial formula to compute?