How to Evaluate Factorials on the TI84 Plus
Did you know you can type an exclamation point on your TI84 Plus calculator? Mathematically, the exclamation point is called a factorial. Usually students learn about factorials in prealgebra 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 [4] to choose the factorial symbol (it looks like an exclamation point.)
There are more MATH submenus available on the TI84 Plus C, if you use the TI84 Plus, pay attention to the name of the submenu and use the left and rightarrow keys to navigate to the correct one.

Press [ENTER] to evaluate the factorial.