Inequality Word Problems

Real-world problems using inequalities

Inequality Word Problems

Key Phrases for Inequalities

| Phrase | Symbol | |--------|--------| | "at least", "minimum", "no less than" | \geq | | "at most", "maximum", "no more than" | \leq | | "more than", "greater than" | >> | | "less than", "fewer than" | << |

Strategy

  1. Define a variable
  2. Write an inequality from the problem
  3. Solve the inequality
  4. Check if the answer makes sense in context

Common Scenarios

Budget problems: Total cost ≤ available money

Grade problems: Average score ≥ desired grade

Capacity problems: Number of people ≤ maximum capacity

Interpreting Solutions

Remember to consider realistic constraints:

  • Can't have negative people
  • Can't work negative hours
  • Round to whole numbers when appropriate

📚 Practice Problems

1Problem 1easy

Question:

Sarah wants to buy notebooks that cost $3 each. She has $20. What is the maximum number of notebooks she can buy?

💡 Show Solution

Let nn = number of notebooks

The cost must be at most $20: 3n203n \leq 20

Divide by 3: n2036.67n \leq \frac{20}{3} \approx 6.67

Since she can't buy a fraction of a notebook: n6n \leq 6

Answer: Maximum of 6 notebooks

2Problem 2medium

Question:

A taxi charges $5 plus $2 per mile. You have $25. What is the maximum distance you can travel?

💡 Show Solution

Let mm = miles traveled

Total cost: 5+2m5 + 2m

This must be at most $25: 5+2m255 + 2m \leq 25

Subtract 5: 2m202m \leq 20

Divide by 2: m10m \leq 10

Answer: Maximum distance is 10 miles

3Problem 3hard

Question:

Maria scored 85, 92, and 88 on her first three tests. What must she score on the fourth test to have an average of at least 90?

💡 Show Solution

Let xx = score on fourth test

Average formula: 85+92+88+x490\frac{85 + 92 + 88 + x}{4} \geq 90

Multiply both sides by 4: 85+92+88+x36085 + 92 + 88 + x \geq 360 265+x360265 + x \geq 360

Subtract 265: x95x \geq 95

Answer: She must score at least 95 on the fourth test