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Project AMP Dr. Antonio R. Quesada Director, Project AMP

    Inquiry Lesson: Loan Payments and Compound Interest


    Students will investigate change related to interest rates and loan payments.

    Using a TI-84 calculator the students will learn to manipulate values using the finance

    application “TVM Solver” which will provide a realistic introduction to the world of

    financial decision-making.


    Americans today live in a fast-paced world in which time is money. One major fault

    with the American consumer is that they do not take the time to investigate where their

    money is going. Most consumers have not learned how to manage money in a responsible

    way and as a result, consumer debt is a growing problem across the country. The

    following statistics have been collected from various government agencies:

    ? According to the Federal Reserve, outstanding non-secured consumer debt rose to 1.65

    trillion in 2001. (Most non-secured debt can be found on credit cards.)

    ? The U.S. Census Bureau and the Federal Reserve report that (non-mortgage) consumer

    debt has increased from an average of $8500 to $14,500.

    ? The Average American household has between 7 and 10 Credit cards (an increase from

    4.21 credit cards in 1999) according to Transunion LLC, 2002, “Consumer Credit


    ? According to the American Bankruptcy Institute, 302,829 people filed for bankruptcy in


    ? On average, the typical credit card purchase is 112% higher than if cash were used for the


    ? Over 40% of U.S. families spend more than they earn. (Federal Reserve)

Vocabulary Terms:

    Number of payments the number of payments in a given period of time, usually

    the months that the loan payments will be made. (N)

    Interest rate the percentage that is used to calculate the additional sum of money

    to be paid when a loan is acquired in addition to the original loan value. (I %)

    Principle value - the original amount of a loan, or initial deposit of an investment (PV)

    Payment the amount of money to be paid within a specific period of time (PMT)

    Future Value - a sum of money that is to be attained through investments (FV)

    Payments per Year - the number of payments in one year (P/Y)

Project AMP Dr. Antonio R. Quesada Director, Project AMP

    Compounded per Year - the number of times interest is calculated on the total

    value of the loan or investment in one year (C/Y)

Background Knowledge:

     Students should be familiar with calculator keypad functions and have a general

    understanding of interest. The students should also have a basic understanding of loans

    and the rationale for saving money.

Ohio Benchmarks (8-10):

     Patterns, Functions and Algebra

    D. Use algebraic representations such as tables, graphs, expressions,

    functions and inequalities, to model and solve problem situations

    Indicator(s) Analyzing Change

    16. Use graphing calculators or computers to analyze change;

    interest compounded over time as a nonlinear growth pattern.

Learning Objectives:

    1. Students will learn to manipulate payment values and interest rates using the

    “Financial TVM Solver” application on the TI-83/TI-84.

    2. Students will develop a number sense related to the manipulation of payment

    amounts, time periods, and interest rates.

    3. Students will gain a basic understanding of personal finance that should

    stimulate further discussion and exploration related to money matters.


    Graphing Calculator with “TVM Solver” financial application loaded in the applications,

    Lesson Worksheets, pencil


    1. Introduce the application as a whole group lesson so that students are familiar

    with the terms and calculator functions

    2. Have students follow along using the screen shots provided in the worksheet

    for the whole group lesson.

    3. Students will team together to solve the remaining problems in the

    investigation using the lab worksheets.


    Informal Assessment - Allow time at the end of class for a whole group

    discussion that will allow students to share their discoveries and determine how

    this activity will influence their money management decisions in the future.

    Project AMP Dr. Antonio R. Quesada Director, Project AMP

    The Lesson

    Introduction “TVM Solver

    1. Turn on the TI-84 and select the “APPS” button.

    2. Choose option 1 “Finance” and hit enter. (Fig. 1)

     (Fig. 1)

    3. Under “CALC” select option 1 “TVM Solver…” and push enter (Fig. 2)

     (Fig. 2)

    4. Calculate the monthly payments for a 5-year loan totaling $25,000 with

    interest compounded monthly at a rate of 5%. Notice that 12 months per year

    multiplied by 5 years would yield 60 months total for the loan. Input the

    following values into the application: N = 60, I%=5, PV=25000, (Leave PMT

    at zero for now), FV=0 (The future value is zero because the loan is being

    paid off), P/Y =12, C/Y=12. see (Fig.3)


    5. In order to calculate the “PMT” (the monthly payment) use the arrow cursor

    and highlight the 0 in “PMT= 0”.

Project AMP Dr. Antonio R. Quesada Director, Project AMP

    6. In order to solve for “PMT”, push the “Alpha” button and then push “Enter”

    to activate the solve function which will calculate the monthly payment.

    Refer to (Fig. 4) and check your values for accuracy.

     (Fig. 4)

    7. Notice that the PMT value is 471.78084, the reason for this is that the

    calculator computes each payment by subtracting from the principal value.

    The value of the monthly payment is really $471.78.

    (The number of place values can be limited to two places by selecting “Mode”

    and then selecting 2 under “Float.”)

Now try the following activities using the Financial “TVM Solver” application.

    Which Car Can I afford?

    You want to buy a car. You go to a car dealer and start looking around. One of

    his first questions that you need to consider is “How much money do you want your

    monthly payment to be?” You, as the consumer may be thinking that a car loan with a

    lower monthly payment means that the car is cheaper. There are a variety of loan options

    available so the length of the loan and the interest rates must also be considered.

    Do you think that it is always a good idea to choose a loan with lowest monthly

    payment? Why is it necessary to consider the length of time that you will be making

    payments on the loan? Write your response below and justify your reasoning:




Project AMP Dr. Antonio R. Quesada Director, Project AMP



    In order to purchase a car for this activity, you must take out a car loan. You could buy a

    2007 Mustang GT Premium Convertible for 31,840 or a 2003 Mustang GT Premium

    Convertible for 19,120. Which loan offers the better value and is affordable?

2007 Mustang GT Premium Convertible 2003 Mustang GT Premium Convertible

     $31, 840 $19,120

Calculate the missing values for both a 3-year loan and a 5-year loan.

     2007 Mustang 2003 Mustang

    3-year loan at 6.5% 5-year loan at 7.15% Table 1.

    Number of Months

    Interest (%)

    Principal Value Monthly Payment

Based on the data collected in Table 1, which car loan payment appears to be a better

    value? ___________________________________________________________

    Why did you choose that loan? Explain your reasoning.



    In your opinion, which loan will result in the greatest amount of savings when the loan

    has been paid off?



    Can the total loan value of each vehicle be determined at this point or do you need more

    information? __________________________________________________________.

Project AMP Dr. Antonio R. Quesada Director, Project AMP

You tell the car salesperson that you really were thinking of a lower monthly payment

    than either of the previous figures. He says, “No problem, we can lower the 5-year loan payment by about $40.” You are quite relieved; however your new loan will have a term

    of 6 years instead of 5 years. You now have an affordable payment but how will this deal

    affect you financially in the future? What do you think?



Complete the table below. In order to calculate the total price (sum of all loan payments),

    multiply the monthly payment by the number of months. To find the amount of interest

    paid, find the difference (subtract) between the principal value and the total price.

    5 year loan at 7.15 6 year loan at 8.2% Table 2. 2003 Mustang

    Number of Months

    Interest (%)

    Principle Value

    Monthly Payment

    Total Price

    Interest Paid

By lowering your monthly payment how much extra did you have to pay on your loan?

    Find the difference between the “Total Price” of both loans. __________________

Why was the salesperson so eager to extend the length of time to pay off your loan? Who

    benefits from this deal over time? Is this fair?





Project AMP Dr. Antonio R. Quesada Director, Project AMP

Now let us consider some new loan options from a local bank to purchase the 2003

    Mustang that had a price tag of $19,120.

    3 year loan at 5 year loan at 6 year loan at Table 3. Local Bank

    6.25% 7.5% 8.75% Loans

     Number of Months

     Interest (%)

     Principle Value

     Monthly Payment

     Total Price

     Interest Paid

Which loan is the best value? Why?




    Why would a person get a car loan with a high interest rate? Is it logical?





    Do you think that people need to understand how interest is calculated on the loans they

    borrow? Why is it important?





Project AMP Dr. Antonio R. Quesada Director, Project AMP


    Now let’s try something else. Assume that you have decided to go with the 6 year loan at 8.75% because you need the lowest payment. You just received an hourly raise at work

    and decide that you can afford to pay an additional $30 each month on your car payment

    beginning with the first payment.

How do you think this will that affect the number of payments?



    To calculate the new number of payments using the “TVM Solver” application, leave the “N” = 0 and allow the calculator to solve for “N” (Remember to highlight the “N= 0” and

    push “Alpha” and “Enter” to solve).

Instead of the loan taking 72 months it will be paid off in _______ months.

    How much money would be saved in interest? ___________.

Making a Down payment:

Another option that can be done is to make a down payment, which is to pay a sum of

    money to the lender at the beginning of the loan. Let’s say that you want to put down a

    $2000 down payment for the car. A car dealer’s loan advisor may tell you …

    “It won’t make a significant difference for your loan payments!”

    Let’s investigate whether or not this statement is valid.

Using the 6 year loan data, apply a down payment of $2000. Notice that you will only

    need to borrow $17,120 for the loan.

What would the new monthly payment be? ____________________

How much did this reduce the monthly payment? _________________

How much money would be saved in interest? ____________

Is the amount of money saved in interest “significant” to you? Who loses money when

    you make a down payment?


Project AMP Dr. Antonio R. Quesada Director, Project AMP

    ________________________________________________________________________________________________________________________________________________ Reflection:

    Describe what you have learned throughout this investigation. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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