Perhaps a dumb math question, but what's the math formula for this?

Lets say I have 2 words and they have to be in the right order,

1. A
2. B

1. B
2. A

It took me 2 guesses/attempts, one of them is the right order. What if it was 10 words? how many attempts would it take me? for instance

1. a
2. b
3. c
4. etc
5.etc
6.
7.
8.
9.
10.