Texas Instruments TI-89 Titanium

Activities 109
Time-Value-of- Money Function
In the Program Editor, define the following Time-Value-of-Money (tvm)
function where temp1 = number of payments, temp2 = annual interest
rate,
temp3 = present value, temp4 = monthly payment, temp5 = future
value, and temp6 = begin- or end-of-payment period (1 = beginning of
month, 0 = end of month).
Note: You can use your computer keyboard to type lengthy text and
then use TI Connect™ software to send it to the TI-89 Titanium.
Finding the Monthly Payment
Find the monthly payment on 10,000 if you make 48 payments at 10%
interest per year.
:tvm(temp1,temp2,temp3,temp4,temp5,temp6)
:Func
:Local tempi,tempfunc,tempstr1
:Ltemp3+(1+temp2/1200temp6)temp4((1N(1+temp2/1200)^
(Ltemp1))/(temp2/1200))Ntemp5(1+temp2/1200)^(Ltemp1)
!tempfunc
:For tempi,1,5,1
:"temp"&exact(string(tempi))!tempstr1
:If when(#tempstr1=0,false,false,true) Then
:If tempi=2
:Return approx(nsolve(tempfunc=0,#tempstr1) | #tempstr1>0
and
#tempstr1<100)
:Return approx(nsolve(tempfunc=0,#tempstr1))
:EndIf
:EndFor
:Return "parameter error"
:EndFunc
On the Home screen, enter the tvm values to
find
pmt.
Result: The monthly payment is 251.53.