Math Problem Statement

Melissa invests $8,200 in two accounts paying 7% and 8% annual interest, respectively. After one year, the total interest earned is $609. How much was invested in each account?

Solution

The image shows a math problem involving simple interest. Here's a summary of the problem:

Problem Statement:

  • Melissa has invested $8,200 in two accounts. One account pays 7% annual interest, and the other pays 8% annual interest.
  • After one year, the total interest earned from both accounts is $609.

You need to determine how much money Melissa invested in each account. Let xx represent the amount invested at 7%, and yy represent the amount invested at 8%.

Equations:

  1. x+y=8200x + y = 8200 (since the total amount invested is $8,200)
  2. 0.07x+0.08y=6090.07x + 0.08y = 609 (since the total interest earned is $609)

To Solve:

You can use the substitution or elimination method to solve the system of equations.

Let's solve this step-by-step using substitution:

  1. From the first equation:
    y=8200xy = 8200 - x

  2. Substitute yy into the second equation:
    0.07x+0.08(8200x)=6090.07x + 0.08(8200 - x) = 609

  3. Distribute and combine like terms:
    0.07x+6560.08x=6090.07x + 656 - 0.08x = 609

    Simplifying:
    0.01x+656=609-0.01x + 656 = 609

  4. Isolate xx:
    0.01x=609656-0.01x = 609 - 656
    0.01x=47-0.01x = -47
    x=470.01=4700x = \frac{-47}{-0.01} = 4700

So, Melissa invested $4,700 at 7%.

  1. Substitute x=4700x = 4700 into y=8200xy = 8200 - x:
    y=82004700=3500y = 8200 - 4700 = 3500

Melissa invested $3,500 at 8%.

Final Answer:

  • $4,700 was invested at 7%.
  • $3,500 was invested at 8%.

Would you like a more detailed explanation, or do you have any questions?

Related Questions:

  1. How can you use the elimination method to solve the same system of equations?
  2. What would the interest be if Melissa had invested the entire $8,200 at 7%?
  3. What is the significance of the different interest rates in this problem?
  4. How would the investment amounts change if the total interest earned was $700 instead of $609?
  5. Can this type of problem be solved graphically? If so, how?

Tip:

When dealing with percentage problems, always ensure that you convert percentages to their decimal forms before performing calculations.

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Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Equations
Simple Interest Calculation

Formulas

Simple Interest = Principal x Rate x Time
System of Equations

Theorems

Linear Combination (Substitution or Elimination Methods)

Suitable Grade Level

Grades 8-10