Math Problem Statement

Financial advisors say that the maximum amount of a person’s house payment (monthly) should be no more than 25% of their monthly salary. If a couple has a total salary of $44,000 per YEAR (divide by 12 to find their monthly salary): ● Determine their maximum monthly house payment allowable; and ● Based on the payment found above, and using an interest rate of 5%, determine the maximum loan amount they qualify for both a (a) 30-year and (b) 15-year mortgage

Solution

To solve this, let's break it into steps:

Step 1: Find the couple's monthly salary

Their total annual salary is $44,000. To find their monthly salary: Monthly Salary=44,00012=3,666.67\text{Monthly Salary} = \frac{44,000}{12} = 3,666.67

Step 2: Determine the maximum allowable monthly house payment

Financial advisors recommend that the house payment should not exceed 25% of the monthly salary. So, we calculate: Max Monthly House Payment=0.25×3,666.67=916.67\text{Max Monthly House Payment} = 0.25 \times 3,666.67 = 916.67 This means their maximum allowable monthly house payment is $916.67.

Step 3: Use the payment to find the maximum loan amount for a 30-year and 15-year mortgage

We use the following formula to calculate the loan amount based on the monthly payment: M=Pr(1+r)n(1+r)n1M = P \frac{r(1+r)^n}{(1+r)^n-1} Where:

  • MM = monthly payment ($916.67),
  • PP = loan amount (which we are solving for),
  • rr = monthly interest rate (annual rate divided by 12),
  • nn = total number of payments (loan term in years multiplied by 12 months).

a) For a 30-year mortgage at 5% interest

  • r=5%12=0.004167r = \frac{5\%}{12} = 0.004167,
  • n=30×12=360n = 30 \times 12 = 360 months.

Now solve for PP: 916.67=P×0.004167(1+0.004167)360(1+0.004167)3601916.67 = P \times \frac{0.004167(1+0.004167)^{360}}{(1+0.004167)^{360}-1} Let's simplify and solve for PP: P=916.67×[(1.004167)3601]0.004167(1.004167)360P = \frac{916.67 \times \left[(1.004167)^{360} - 1\right]}{0.004167(1.004167)^{360}}

b) For a 15-year mortgage at 5% interest

  • r=0.004167r = 0.004167,
  • n=15×12=180n = 15 \times 12 = 180 months.

Similar to the previous case, we solve for PP: 916.67=P×0.004167(1+0.004167)180(1+0.004167)1801916.67 = P \times \frac{0.004167(1+0.004167)^{180}}{(1+0.004167)^{180}-1}

I will compute the loan amounts for both cases next.### Results:

  • For a 30-year mortgage at 5% interest, the couple qualifies for a maximum loan amount of approximately $170,759.
  • For a 15-year mortgage at 5% interest, the couple qualifies for a maximum loan amount of approximately $115,918.

Would you like further details on any part of this process or clarification on the calculations?

Here are some related questions to explore:

  1. How would a higher interest rate affect the maximum loan amount?
  2. What if the couple could afford 30% of their monthly income for a house payment?
  3. How does a 20-year mortgage compare in terms of maximum loan amount?
  4. What happens if their combined salary increases to $60,000 per year?
  5. How does an adjustable-rate mortgage (ARM) differ from a fixed-rate mortgage?

Tip: When interest rates rise, opting for a shorter mortgage term like 15 years reduces total interest paid, even if the monthly payment is higher!

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Math Problem Analysis

Mathematical Concepts

Percentages
Loan Amortization
Interest Rates

Formulas

Max Monthly House Payment = 0.25 × Monthly Salary
Loan Amortization Formula: M = P × [r(1+r)^n / ((1+r)^n - 1)]

Theorems

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Suitable Grade Level

Grades 11-12