Applications of Systems - Worksheet 4 - 9th Grade

Medium

Apply systems of equations to solve real-world problems (Medium)

12 problems · 25-30 minutes · Skills: systems, problem solving, modeling

About This Worksheet

This medium-level worksheet contains 12 problems designed for 9th Grade students practicing applications of systems. Medium worksheets introduce larger numbers and varied question formats to deepen understanding and build fluency.

Systems applications show why algebra was developed — to solve problems that arithmetic alone cannot. Break-even analysis, mixture problems, and rate problems all reduce to systems. Building proficiency here prepares students for STEM coursework, business mathematics, and standardized tests.

  • Define two variables for two unknowns in a contextual problem
  • Write a system of two equations from given conditions
  • Solve and interpret the solution, including checking whether it satisfies all original conditions
  • Translate verbal descriptions of rates, mixtures, and costs into algebraic equations
  • Evaluate whether the answer makes sense in the real-world context of the problem

How to Solve: Worked Example

Example Problem: A jar has 18 coins, all quarters and dimes, worth $2.55. How many quarters?
Solution Steps:
  1. Let q be quarters and d dimes: q + d = 18.
  2. Work in cents for the value equation: 25q + 10d = 255.
  3. Substitute d = 18 - q: 25q + 10(18 - q) = 255.
  4. 25q + 180 - 10q = 255, so 15q = 75 and q = 5.
Answer: 5 quarters
Tip: Convert dollars to cents before writing the value equation — it keeps everything in whole numbers.
1
A jar has 25 coins, all quarters and dimes, worth $4.45. How many quarters?
2
A jar has 17 coins, all quarters and dimes, worth $2.90. How many quarters?
3
A jar has 10 coins, all quarters and dimes, worth $1.75. How many quarters?
4
A jar has 20 coins, all quarters and dimes, worth $3.95. How many quarters?
5
A jar has 15 coins, all quarters and dimes, worth $2.70. How many quarters?
6
A jar has 13 coins, all quarters and dimes, worth $2.35. How many quarters?
7
A jar has 26 coins, all quarters and dimes, worth $4.25. How many quarters?
8
A jar has 19 coins, all quarters and dimes, worth $3.85. How many quarters?
9
A jar has 9 coins, all quarters and dimes, worth $1.65. How many quarters?
10
A jar has 14 coins, all quarters and dimes, worth $2.00. How many quarters?
11
A jar has 19 coins, all quarters and dimes, worth $3.70. How many quarters?
12
A jar has 13 coins, all quarters and dimes, worth $2.50. How many quarters?

Answer Key

1. 132. 83. 54. 135. 86. 77. 118. 139. 510. 411. 1212. 8

Frequently Asked Questions

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How do I find worksheets at different difficulty levels?

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What skills does this systems of equations & inequalities worksheet cover?

This worksheet focuses on systems, problem solving, modeling. It is designed for 9th Grade students and provides structured practice through varied problem types with a worked example to guide students before they begin.

Can I use this worksheet in my classroom?

Yes. All worksheets on K12Worksheets are free for classroom use. You can print copies for your entire class. With 10 worksheets per subtopic at three difficulty levels, you have plenty of options for differentiated instruction and individualized practice.

How many problems are on this worksheet?

This worksheet contains 12 problems. It typically takes 25-30 minutes to complete. An answer key with all solutions is included so parents and teachers can check work quickly.