# How many ways can Ismail arrange four different textbooks on the shelf in his locker?

Oct 23, 2016

4! =24

#### Explanation:

There are $4$ different choices for the first book, but once that one is in place, there are $3$ choices for the second, two for the third and then only 1 book remains to be placed on the shelf last.
This assumes that the books are all different.

The number of possible arrangements is $4 \times 3 \times 2 \times 1 = 24$

This is called '4 factorial' and has the symbol 4!