If the keys are dirty, you can take it apart and clean using the link below.
This may void your warranty, so you may wish to call TI first and see if they will replace it for you.
Well since you asked this question you must of used the keys on your laptop/computer! So you must of had the sense to count them...Total Keys = 84, but it depends on what computer you have....
48+84+84=216
The total is 252
4 plus 80 = 84
420
84
Press the APPS button. You will see a list of all the applications that are currently on the TI-84 plus. Use the arrow keys to scroll down to the one you want to use and then press ENTER.
on a typical keyboard you can find 84 keys
96 plus 48 plus 84 is equal to 228.
26 plus 16 plus 84 is equal to 126.
84
84