Math Problem Statement

Write the system of 3 linear equations in 3 variables that is described by the following:  A person invested $17,000 for one year, part at 10%, part at 12%, and the remainder at 15%.  (These are annual interest rates, not compounded in any way.)  The total annual income from these investments was $2110.  The amount of money invested at 12% was $1000 less than the amount invested at 10% and 15% combined

Solution

To write the system of equations for this situation, we need to define variables and translate the problem into mathematical equations:

Variables

Let:

  • xx: The amount of money invested at 10%.
  • yy: The amount of money invested at 12%.
  • zz: The amount of money invested at 15%.

Key Information and Equations

  1. Total investment: The total amount invested is $17,000. x+y+z=17000x + y + z = 17000

  2. Total income: The total annual income from these investments is $2110. The income is calculated using the interest rates: 0.10x+0.12y+0.15z=21100.10x + 0.12y + 0.15z = 2110

  3. Relationship between investments: The amount invested at 12% (yy) is $1000 less than the sum of the amounts invested at 10% (xx) and 15% (zz). y=x+z1000y = x + z - 1000

Final System of Equations

1. & \quad x + y + z = 17000 \\ 2. & \quad 0.10x + 0.12y + 0.15z = 2110 \\ 3. & \quad y = x + z - 1000 \end{aligned}$$ Would you like me to solve this system or explain it further? --- Here are 5 related questions to expand your understanding: 1. How do we solve systems of linear equations using substitution or elimination? 2. What happens if we graph these equations? How can we interpret the solution geometrically? 3. How would the system change if the annual income or interest rates were different? 4. Can this system of equations have more than one solution? Why or why not? 5. What is the importance of defining variables correctly in word problems? **Tip:** Always organize the problem's information into clear variables and translate step by step into mathematical equations for clarity!

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Math Problem Analysis

Mathematical Concepts

Linear Equations
Systems of Equations
Interest Calculation

Formulas

x + y + z = Total Investment
0.10x + 0.12y + 0.15z = Total Annual Income
y = x + z - Offset

Theorems

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Suitable Grade Level

Grades 9-12