How to Evaluate Factorials on the TI-84 Plus
Did you know you can type an exclamation point on your TI-84 Plus calculator? Mathematically, the exclamation point is called a factorial. Usually students learn about factorials in pre-algebra and then forget what they are by the time they need to use factorials to solve tough probability problems. Here is a quick refresher on factorials.
4! = 4*3*2*1 and 7! = 7*6*5*4*3*2*1. If you haven’t done so already, press [2nd][MODE] to get to the Home screen. Follow these steps to type a factorial in your calculator:
Enter the number you would like to take the factorial of.
Press the following keys to access the Math Probability menu
and press  to choose the factorial symbol (it looks like an exclamation point.)
There are more MATH submenus available on the TI-84 Plus C, if you use the TI-84 Plus, pay attention to the name of the submenu and use the left- and right-arrow keys to navigate to the correct one.
Press [ENTER] to evaluate the factorial.