Math Problem Statement

Jeffrey's student loan of $28,500 at 3.62% compounded quarterly was amortized over 3 years with payments made at the end of every month. What was the principal balance on the loan after 1 year? Round to the nearest cent

Solution

To find the principal balance on Jeffrey's loan after 1 year, we need to follow these steps:

Step 1: Identify the relevant parameters

  • Principal (P): $28,500
  • Annual interest rate (r): 3.62% or 0.0362
  • Compounding frequency: Quarterly (4 times a year)
  • Loan term (n): 3 years
  • Payment frequency: Monthly (12 times a year)

Step 2: Convert the annual interest rate to the quarterly interest rate

The nominal quarterly interest rate ii can be calculated as: i=r4=0.03624=0.00905i = \frac{r}{4} = \frac{0.0362}{4} = 0.00905

Step 3: Calculate the number of quarterly periods in 3 years

The number of quarters in 3 years is: nquarters=3×4=12 quartersn_{\text{quarters}} = 3 \times 4 = 12 \text{ quarters}

Step 4: Calculate the monthly payment

To find the monthly payment, we use the amortization formula: PMT=P×i1(1+i)nmonthsPMT = \frac{P \times i}{1 - (1 + i)^{-n_{\text{months}}}} where:

  • PP is the principal amount,
  • ii is the monthly interest rate, and
  • nmonthsn_{\text{months}} is the total number of payments (36 months).

However, since the interest is compounded quarterly, the effective monthly interest rate jj is: j=(1+r4)131=(1+0.00905)131j = \left(1 + \frac{r}{4}\right)^{\frac{1}{3}} - 1 = \left(1 + 0.00905\right)^{\frac{1}{3}} - 1

Calculating jj: j0.003015j \approx 0.003015

Now calculate the monthly payment PMTPMT: PMT=28500×0.0030151(1+0.003015)36PMT = \frac{28500 \times 0.003015}{1 - (1 + 0.003015)^{-36}} PMT828.25PMT \approx 828.25

Step 5: Calculate the principal balance after 1 year

After 1 year (12 payments), the remaining balance can be found using the amortization formula: B=P×(1+j)12PMT×(1+j)121jB = P \times (1 + j)^{12} - PMT \times \frac{(1 + j)^{12} - 1}{j} where BB is the remaining balance.

Substitute the known values: B=28500×(1+0.003015)12828.25×(1+0.003015)1210.003015B = 28500 \times (1 + 0.003015)^{12} - 828.25 \times \frac{(1 + 0.003015)^{12} - 1}{0.003015} B28500×1.0368828.25×0.03680.003015B \approx 28500 \times 1.0368 - 828.25 \times \frac{0.0368}{0.003015} B29549.69,900B \approx 29549.6 - 9,900 B19,649.60B \approx 19,649.60

So, the principal balance on the loan after 1 year is approximately $19,649.60.

Would you like more details or have any questions?

Here are some related questions:

  1. How would the remaining balance change if the interest rate were 4%?
  2. What would be the remaining balance after 2 years?
  3. How much total interest would Jeffrey pay over the life of the loan?
  4. How would a higher payment frequency affect the remaining balance?
  5. What would the monthly payment be if the loan term were extended to 5 years?

Tip: To quickly approximate the balance after a certain period, you can use online amortization calculators, which automate the complex formulas.

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Math Problem Analysis

Mathematical Concepts

Amortization
Compound Interest
Monthly Payments

Formulas

Amortization formula

Theorems

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Suitable Grade Level

Advanced High School / College