Math Problem Statement

Jonathan is buying a car today. The car costs R445222 and he can afford to make monthly payments of R12117 at the end of every month. He must pay interest at a rate of 7.947% per year compounded monthly. If the last payment Jonathan makes can be larger than R12117, how many payments must Jonathan make to repay the car loan?

Solution

To solve this problem, we need to determine the number of monthly payments Jonathan needs to make to fully repay the car loan. This involves calculating the total number of payments required for a loan with fixed monthly payments and an interest rate compounded monthly.

Step 1: Identify the given variables

  • Loan amount (Principal, PP): R445,222
  • Monthly payment (RR): R12,117
  • Annual interest rate (rr): 7.947% per year
  • Monthly interest rate (ii): 7.947%12\frac{7.947\%}{12} per month

Step 2: Convert the annual interest rate to a monthly interest rate

i=7.947%12=0.07947120.0066225i = \frac{7.947\%}{12} = \frac{0.07947}{12} \approx 0.0066225

Step 3: Use the loan amortization formula

The loan balance after nn payments is given by:

Pn=P×(1+i)nR×((1+i)n1)iP_n = P \times (1 + i)^n - \frac{R \times ((1 + i)^n - 1)}{i}

Since we need to find the point where the remaining balance PnP_n becomes zero, we rearrange the formula to solve for nn:

P=R×((1+i)n1)i×(1+i)nP = \frac{R \times ((1 + i)^n - 1)}{i \times (1 + i)^n}

Simplifying further, we solve for nn:

(1+i)n=RRP×i(1 + i)^n = \frac{R}{R - P \times i}

n=log(RRP×i)log(1+i)n = \frac{\log \left(\frac{R}{R - P \times i}\right)}{\log(1 + i)}

Step 4: Substitute the values and solve for nn

Substituting the given values:

n=log(12,11712,117445,222×0.0066225)log(1.0066225)n = \frac{\log \left(\frac{12,117}{12,117 - 445,222 \times 0.0066225}\right)}{\log(1.0066225)}

Let's calculate this value.Jonathan needs to make approximately 42.24 payments to repay the car loan. Since the number of payments must be a whole number, he will make 42 regular payments of R12,117, and the final (43rd) payment will be slightly smaller.

Would you like further details or have any questions?

Here are 5 related questions you might consider:

  1. How much will Jonathan's final payment be?
  2. What would happen if the interest rate were different?
  3. How much interest will Jonathan pay over the course of the loan?
  4. How would a down payment affect the number of payments?
  5. What would be the impact if Jonathan increased his monthly payments?

Tip: Understanding how interest compounds on a loan can help you make better financial decisions, especially when it comes to long-term payments.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Loan Amortization

Formulas

Loan Amortization Formula

Theorems

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Suitable Grade Level

Grades 11-12