Factorials,Combinations and Permuatations
on the TI83
221 in the TI83 Guidebook
The TI series calculator performs numerous probability operations.
Factorials
Press 4 .  
Enter the number you want to find the factorial. Then Press 4 . You can also find the factorials of more than one number at a time. Try this... {3, 4, 5} 4 . You should get {6, 24, 120} Press ( to get { key. 

Permutations 

Press 2 .  
Enter the first number. 52 Then Press 2 . Then enter the second number. 5 Press You can also find permutations of more than one number at a
time. Try this... 

Combinations 

Press 3 .  
Enter the first number. 52 Then Press 3 . Then enter the second number. 5 Press You can also find permutations of more than one number at a
time. Try this... 