Effective interest rate

If necessary, press f [FIN] to clear the financial registers.
4 0 0 0 0 PV ( enter present value )
3 . 3 i ( enter interest rate )
4 0 N ( enter number of periods)
FV ( compute future value )

Neely Neel Neel Neelerson,

--> APPS
--> TVM

Viola. The initials TVM stand for Time-Value-Money; it's a widely used tool throughout financial mathematics. If you are looking to deal with annuities, bonds, present value equations, future value equations, or even certain stocks then you will want to use the TVM app within your TI-84.

When you go into that menu screen you will see about 10 input lines; and despite how you're being taught you'd be best off using only five (from a mathematical & conceptual standpoint). The backbone of the TVM is the time-zero equation of value. So, all you want to be touching is the N, I/Y, PV, PMT, and FV keys.

Background on TVM:
N = Number of intervals
I/Y = Effective Interest Rate Per Interval (5% is .05 but the computer wants it entered as 5.0)
PV = The Present Value
PMT = Recurring Payment (either deposit or withdrawal)
FV = Future Value

There are like 3 other inputs that I encourage you to ignore (in exchange for learning exactly what's going on within this application).

NOTE: You MUST make your effective interest term match your number of intervals. For example, an annuity with monthly payments for 5 years with a monthly effective interest rate of 2% would need an N value of 60 (which is 12 months per year times 5 years for a total of 60 months).

There's more that could be said, but I think this should help you find the PV of an annuity.

Go Bulls,



The Math Cheetah
[email protected]

You're entering the interest as a monthly rate. You need to use an annual rate. Instead of .6434 per month, use .6434*12 = 7.7208 for the I/Y value.

Using the calculator at http://www.ecentralcu.org/futurevalue-pp.html I get $35,065.70

Payments = $21,600 + $13,465.70 in interest.

Click APPS and then ENTER for Finance and then ENTER again for the TVM Solver. There you can input the PV, PMT, i, etc.

I'm going to make up an example so this is easier to answer.

Ex: You have a bond with a price of $987, with a coupon of 1.5%, which matures in 10 years.
To do this problem:

[APPS] [1] [1]

What comes up on screen:

N=
I%=
PV=
PMT=
FV=
This is all the stuff that you really care about.

Now, add in the info you know from the equation. Put in a 0 if you don't know the number for that part.

This is what it should look like:
N=10
I%=0
PV=-987
PMT=15
FV=1000

Now, cursor back up to the I%=0 part.
Highlight the '0' that you had in there from before.
[ALPHA] [ENTER] ----> notice above the enter button it says in green lettering "solve", this is what you are trying to do.

Yay! Your caluculator has now figured out the interest rate!
it should say:
I%=1.642027191



Notes:
1. Make sure your payment is set at the end of the period (this is just the standard so you probably don't want to mess with it.) Scroll down to the PMT: END BEGIN part and make sure the END is highlighted.

2. This example used annual coupon payments. The p/y and c/y business is used for when you have semi-annual payments or semi-annual compounding (or daily, or hourly etc). You can use this feature, or you can just adjust the payment and periods
(ie: if this were a semi-annual coupon bond, the N would be 20 and the pmt would be 7.5)

You have the payments-per-year set to 12. For this pair of problems, it needs to be set to 1.
Press 2nd [P/Y] 1 ENTER.

If this is the same manual that you have already ... then apologies!

http://education.ti.com/educationportal/downloadcenter/SoftwareDetail.do?website=US&appId=6115&tabId=2

Are you putting 30x12=360 for N? Since you have monthly payments, you have to compute it a little different. Also, you have to find the effective monthly interest rate. 1.0575^(1/12) = .4669839%.

Another way is to enter 30 for N and 5.57 for I/Y, and change P/Y to 12.

Hope this helps!

Hmmm, I don't think the problem is with your calculator. I'd be checking the accounting question again as I don't think you've got your annuity question structured right.

4 Year Annuity
14% Annual Interest Rate
Your contributing $4,000 per year over the next 4 years
and you already know the future value is $50,069?

You'd have to make annual payments of $11,878.93 (4 of them) at that annual interest rate to get to a future value of $50,069 (which has a present value of $43,632.24).

Are you sure that the FV isn't the trade in value at the end of the 4 years?