Hi! So today we’re talking about factorials in permutations! How exciting! Yes! Recently I had a colleague tell me about the first time she saw exclamation marks on a math quiz! She thought the proctors were just really excited about the numbers! Much to the amusement of her mathematician husband! And … okay, it’s getting annoying so I’ll stop now. But anyway, an exclamation mark after a number actually indicates a factorial, or the product of that number and all the numbers less than it. So, for example,
5! = 5 x 4 x 3 x 2 x 1 = 120.
Or in the case of Tina, lets say there are different dimensions where she can live in one of twelve cities and have one of four jobs and be married or not. Then she technically could find herself involved in as many as 12! x 4! x 2! = 2,299,2076,800 situations, each taking place in a different dimension. Whew! Now, I realize that’s a lot so I cut down drastically on that number and only covered several of them in my books. But I still had people think I covered too many and let it become too confusing. And one didn’t like that she didn’t quite get a happy ending. Now granted, maybe her life isn’t perfect in all the remaining dimensions at the end but she does have her happy moments too. Like in the St. Louis realm, she goes to this cool 80s party and to LA and meets some hunky Hollywood actor types and then goes to the zoo. And who doesn’t like the zoo? Especially a happy zoo?
Well, but anyway – join me next time when I will continue on combinations with factorials and other stuff we can do with them. Hint: prepare to get choosey.