Question

In how many ways can you arrange 5 books in a bookshelf?

Answer 1

`5! =120`

For the first place in your bookshelf, you can choose any of the 5 books. For the second place you have a choice of 4, etc.

The total number of possibilities are thus:

`5*4*3*2*1` which in maths is abbreviated to `5!`
(pronounced as 5 factorial).

`n!` or "n-factorial" means: multiply all numbers from 1 up to and including `n`

Most calculators have an `x!` button. In GC's it's in one of the menus.