Quote:

Would someone show me the formula(s) for these financial calculations so I can put them in a math program!
Such as.. how to solve for each one of these given the value of the others : Present Value, Future Value, Interest Rate, Term, Payment

Thanks in advance :)

I've had this program sitting in my HP15C for a long time now. I've also used close relatives on the HP11C and HP33S. Not as fancy as some of the TVM programs people use, but nice to have ready when trying to talk turkey at a car dealership!

Time Value of Money Calculations for HP-15C
Chris McCormack - 21 Oct 2007

These routine perform loan calculations using the present value

annuity factor, or PVAF. This relates the present value (loan amount)

to the periodic payments necessary to pay it off.

PVAF(r,N) = (1/r)[1-1/(1+r)^N]

In this equation, r is the decimal interest per payment period

(.01 would represent a monthly loan with a 12% rate) and N in the

number of payments (48 would work for a four-year car loan).

Note - Labels 9 and 6 were used because 9 is next to the divide key

(breaking the loan down into payments) and 6 is next to the multiply

key (building up the total loan amount).

Memory Usage: 21 steps

Register usage: R0 = interest rate per period

R1 = number of periods

Label Usage: LBL 9 : calculate payment for a given amount borrowed

LBL 6 : calculate amount borrowed for a given payment

LBL.9 : (internal) determine PVAF

001 LBL 9 // ( LoanAmt -- Payment )

002 GSB .9 / // divide PV by PVAF

004 RTN

005 LBL 6 // ( Payment -- LoanAmt )

006 GSB .9 * // multiply payment by PVAF

008 RTN

009 LBL .9 // ( -- PFAV )

010 RCL 0 1 + // R0 holds interest per period

013 RCL 1 CHS y^x // R1 holds number of periods

016 1 x<>y -

019 RCL 0 /

021 RTN

Sample calculations:

$5000 borrowed at 10% with 36 monthly payments

--> $161.34 / month

$1500/month on a 30 year mortgage at 7.5%

--> $215,526.44 borrowed