Math Problem Statement

A house is bought for R260 000. The buyer pays R50,000 cash and secures a loan for the balance to be repaid monthly over a period of 20 years. If interest is calculated at 19.5% p.a., compounded monthly, what will be the equal monthly payments? 

Solution

To calculate the equal monthly payments for a loan, we use the loan amortization formula:

M=Pi(1+i)n(1+i)n1M = P \frac{i(1+i)^n}{(1+i)^n - 1}

Where:

  • MM = Monthly payment
  • PP = Loan principal (amount borrowed)
  • ii = Monthly interest rate (annual interest rate divided by 12)
  • nn = Total number of payments (loan term in months)

Step 1: Identify the known values

  1. The house cost is R260,000R260,000.
  2. The buyer pays R50,000R50,000 in cash, so the loan principal is: P=R260,000R50,000=R210,000P = R260,000 - R50,000 = R210,000
  3. Annual interest rate (rr) = 19.5%, so the monthly interest rate is: i=19.512×100=0.01625(or 1.625% per month)i = \frac{19.5}{12 \times 100} = 0.01625 \, (\text{or } 1.625\% \text{ per month})
  4. Loan term = 20 years, so the total number of payments is: n=20×12=240monthsn = 20 \times 12 = 240 \, \text{months}

Step 2: Substitute values into the formula

M=210,0000.01625(1+0.01625)240(1+0.01625)2401M = 210,000 \cdot \frac{0.01625(1+0.01625)^{240}}{(1+0.01625)^{240} - 1}

Step 3: Compute the values step-by-step

  1. 1+0.01625=1.016251 + 0.01625 = 1.01625
  2. 1.016252401.01625^{240}: Calculate the compounding factor over 240 months.
  3. Use the formula to find MM.

Let me compute this for you. Given values P = 210000 # Loan principal (R) annual_interest_rate = 19.5 / 100 # Annual interest rate monthly_interest_rate = annual_interest_rate / 12 # Monthly interest rate n = 20 * 12 # Total number of payments (20 years in months)

Loan amortization formula

i = monthly_interest_rate M = P * (i * (1 + i)**n) / ((1 + i)**n - 1)

MThe monthly payment for the loan will be approximately R3,485.30.

Let me know if you need a detailed breakdown of the steps or any clarifications.

Here are 5 related questions you might find useful:

  1. How is the total interest paid over the loan term calculated?
  2. What happens if the interest rate changes during the loan period?
  3. How does a shorter loan term affect monthly payments and total interest?
  4. Can we calculate the outstanding balance after a certain number of payments?
  5. What is the impact of making extra payments toward the principal?

Tip: When planning long-term loans, always consider how changes in interest rates could impact your repayment plan.

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Math Problem Analysis

Mathematical Concepts

Loan Amortization
Compound Interest
Financial Mathematics

Formulas

Loan Amortization Formula: M = P * [i(1+i)^n] / [(1+i)^n - 1]

Theorems

Compound Interest Formula

Suitable Grade Level

Grades 10-12