I wanted to write a simple formula in TI-Basic to calculate compound interest for my TI-84 calculator. The formula for compound interest is A = P(1+(r/n))^(n)(t) where p is the principal amount, r is the interest rate (expressed as a decimal), n is the number of times the principal is compounded, t is the amount of time, and a is your final amount with interest added.
When I set variables (see below) and and type the formula in exactly how it is above on my calculators home screen, I get $7332.86, which is the correct answer.
However, when I set the variables and type the formula in as a program (see below), I get $42684.69, which is not correct.
I have tried this program on 2 different TI-84 calculators and I have gotten the same results, so it is not something with my calculator.
I am honestly stumped. I have no idea why this is happening, so if you are good at math, know how to program a ti series calculator, or just see a mistake that I am missing, please tell me because this thing has been driving me crazy!
Program with same inputs and formula but gives different answer than when used on the home screen:
: 2000 -> P
: 0.065 -> R
: 54 -> N
: 20 -> T
: P(1+(R/N))^(N)(T) -> A
: Disp A
I don't exactly know what the problem you are facing is, but I think your program should look like this:
Prompt P
Prompt R
Prompt N
Prompt T
Disp P(1+(R/N))^(NT)
EDIT
I think you need an extra set of parentheses. ^(N)(T) only raises to the power of N, and then multiplies by T. Try ^((N)(T)) or simply ^(NT).