In my son's Math text, he's been studying compound probability. Recent lessons had him drawing tree diagrams to list possible outcomes of events. He loved this concept, and he desperately wanted to find a way to teach it to his Challenge A class.
There are five students in the class, and they often sit in the same five chairs. He wanted the class to help him discover how many different ways they could be seated around the table. He used what he had learned, as well as making his classmates rotate seats a few times, to show them that there were 120 different ways the 5 of them could sit around the table.
Fortunately, in his preparation, we came across the video above which taught us how to use the Factorial! button on a calculator. My life has been revolutionized. Plus, the video is a lot of fun.