Posted by john on December 26, 1999 at 13:45:30:
Make it a habbit of first punching [2nd] [FIN] [ON/C] just to be sure it’s clear and ready to go.
What is your variable?
Say I want payment on a 100K loan at 7.75% over 30 years.
I need: Interest rate, Length, Amount
keystrokes would be (no need to [ON/C] between):
a) [2nd] [FIN] [ON/C]: clear the calculator
b)  [PV]: giving loan amount, or “pricipal value”
c)  multiply by  [=] [N]: calculate # mos, or periods. If you know it’s 360, just enter  [N].
d) [7.75] divided by  [=] [i%]: calculate monthly interest rate (or interest rate per period)
e) [CPT] [PMT]: gives you your payment amount.
f) hey, how much do you still owe after 36 months of payments? Do this:  [2nd] [bal]: give you balance after 36 months. You can [ON/C] after this and figure a different # of months too.
Remember, you want the unknown. All needed components are: PV: present value, %i: interest per period, N: number of periods(or payments), PMT: payment. Enter the three you have, then [CPT] the one you don’t have.
- Also, you may need to convert APR interest rate to EFF. To convert it, [ON/C]  (number of periods)[2nd] [APR] [8.75] (if APR is 8.75%)[=] (gives you EFF).
2nd = like a shift key to use RED instructions printed above buttons.
N = number of periods, period = 1 month if payments are monthly. Call it number of payments to keep it simple.
i% = interest rate each compounding period. so if a period is one month, i% is the yearly interest divided by 12.
PMT = Payment amount
PV = principal Value. Amount of loan. (FV=future value)
Hope I havn’t botched this up too bad…
Also check out TI’s FAQ’s at: http://www.ti.com/calc/docs/faqba35main.htm