We're counting all of the different ways that the same number of cards can be arranged. So in order to, I guess, not over-count, we have to divide this by the way 9 cards can be rearranged. So how many ways can 9 cards be rearranged? If I have 9 cards, and I'm going to pick one of 9 to be in the first slot, well, that means I have 9 ways to put something in the first slot. Then in the second slot, I have 8 ways of putting a card in the second slot, because I took 1 to put in the first, so I have 8 left, then 7, then 6, then 5, then 4, then 3, then 2, then 1. That last slot, there's only going to be one card left to put in it. So this number right here, where you take 9 times 8 times 7 times 6 times 5 times 4 times 3 times 2 times 1, or 9, you start with 9, and then you multiply it by every number less than 9, every, I guess we could say, natural number less than 9, this is called 9 factorial.