Math Problem Statement

The given amount of annual interest is earned from a total of $13,000 invested in two funds paying simple interest. Write and solve a system of equations to find the amount invested at each given rate.

Solution

The problem in the image asks to write and solve a system of equations based on the given simple interest situation:

  1. Total investment is $13,000.
  2. The interest generated is $500 per year.
  3. The interest rates are 2% and 5%.

Define variables:

  • Let xx be the amount invested at 2%.
  • Let yy be the amount invested at 5%.

We know:

  • x+y=13,000x + y = 13,000 (the total amount invested is $13,000).
  • The interest from each part is calculated using simple interest formula I=P×rI = P \times r, where PP is the principal and rr is the rate.
  • The total interest earned is $500. So, the interest equation is: 0.02x+0.05y=5000.02x + 0.05y = 500

System of equations:

  1. x+y=13,000x + y = 13,000
  2. 0.02x+0.05y=5000.02x + 0.05y = 500

Solving the system:

Step 1: Solve for yy in terms of xx from the first equation:

y=13,000xy = 13,000 - x

Step 2: Substitute y=13,000xy = 13,000 - x into the second equation:

0.02x+0.05(13,000x)=5000.02x + 0.05(13,000 - x) = 500 Expand the equation: 0.02x+0.05×13,0000.05x=5000.02x + 0.05 \times 13,000 - 0.05x = 500 0.02x+6500.05x=5000.02x + 650 - 0.05x = 500 Combine like terms: 0.03x+650=500-0.03x + 650 = 500 Solve for xx: 0.03x=500650-0.03x = 500 - 650 0.03x=150-0.03x = -150 x=1500.03=5,000x = \frac{-150}{-0.03} = 5,000

Step 3: Solve for yy:

y=13,0005,000=8,000y = 13,000 - 5,000 = 8,000

Conclusion:

  • The amount invested at 2% is $5,000.
  • The amount invested at 5% is $8,000.

Would you like further details or have any questions about this?

Here are 5 questions to deepen understanding:

  1. How would the equations change if the total investment were different?
  2. What happens if both interest rates were the same?
  3. Can you use substitution or elimination to solve this system?
  4. How does the simple interest formula change if the time is more than 1 year?
  5. What if the total interest earned was $600 instead of $500?

Tip: Always check your solution by substituting the values back into both original equations to ensure they satisfy both conditions.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Equations
Simple Interest

Formulas

Simple interest formula: I = P * r
System of linear equations: x + y = 13,000, 0.02x + 0.05y = 500

Theorems

Solving systems of linear equations by substitution

Suitable Grade Level

Grades 8-10