00:01
We have the letters a through f, that is a, b, c, d, e, f.
00:04
We're going to be making some three letter codes, but we're not allowed to repeat any letters.
00:10
So how many different codes can we make? well, for the first letter, we have six options.
00:14
It could be a, b, c, d, e, or f.
00:17
So i'll write a six here.
00:19
The second letter, however, only has five options.
00:22
That is, if we chose a for the first letter, the second letter could only be b, c, d, or f, five options...