00:01
They give us the word rock, which has the letters r -o -c -k, and we want to know the number of ways we can arrange all the letters in this word.
00:09
So we have four letters.
00:13
How many ways? now, the order we put it in is going to matter.
00:16
So we have four ways that we can pick that first letter.
00:19
Once we do, it's gone.
00:21
Then we have three ways we can pick the next letter.
00:24
Once we do, that's gone.
00:26
The two ways to pick the next letter, once we do that, then we only have one way to pick the last letter.
00:32
We multiply these together...