πŸ“ Inequalities

Cambridge Lower Secondary Β· Grade 7 Β· Algebra

Symbols
x > 3  Β·  x < βˆ’1  Β·  x β‰₯ 5  Β·  x ≀ 0
Greater than Β· Less than Β· At least Β· At most
Solving
2x ≀ 10  β†’  x ≀ 5
Divide both sides (same direction)
Flip Rule ⚠️
βˆ’3x > 12  β†’  x < βˆ’4
Divide by negative β†’ flip the symbol!

Which symbol fits? Click to reveal! 🍬

What you'll learn:

  • Inequality symbols: <, >, ≀, β‰₯ and their meanings
  • Showing inequalities on a number line (open/closed circles)
  • Solving one-step inequalities: x + 3 > 7, 2x ≀ 10
  • Solving two-step inequalities: 3x βˆ’ 2 > 10
  • Flipping the inequality when dividing by a negative number
  • Integer solutions: list all integers satisfying βˆ’2 < x ≀ 5
  • Writing inequalities from word problems

πŸ“– Learn: Inequalities

Part 1: Inequality Symbols

An inequality compares two values and tells us one is bigger, smaller, or equal to the other.

SymbolMeaningExampleRead as
<Less thanx < 5"x is less than 5"
>Greater thanx > βˆ’2"x is greater than βˆ’2"
≀Less than or equal tox ≀ 8"x is at most 8"
β‰₯Greater than or equal tox β‰₯ 0"x is at least 0"
πŸ’‘ Memory trick: the open end of the symbol always points to the bigger number. Think of it as a hungry mouth eating the larger value: 3 < 7 β€” the mouth opens toward 7.

Part 2: Number Lines

We show inequalities on a number line using circles and arrows:

  • Open circle β—‹ β€” the value is not included (strict inequality: < or >)
  • Closed/filled circle ● β€” the value is included (≀ or β‰₯)
  • The arrow points in the direction of all values that satisfy the inequality
x > 2 βˆ’3 βˆ’2 βˆ’1 0 1 2 3 4 5 6 7 open β—‹ x ≀ βˆ’1 closed ●

Part 3: Solving One-Step Inequalities

Solve an inequality the same way you solve an equation β€” do the same operation to both sides.

Solve x + 3 > 7: subtract 3 from both sides β†’ x > 4
Solve 2x ≀ 10: divide both sides by 2 β†’ x ≀ 5
Solve x βˆ’ 4 β‰₯ βˆ’1: add 4 to both sides β†’ x β‰₯ 3
πŸ’‘ The inequality symbol stays the same as long as you add, subtract, multiply or divide by a positive number.

Part 4: Solving Two-Step Inequalities + The Flip Rule

Use two steps β€” same as solving two-step equations.

Solve 3x βˆ’ 2 > 10: add 2 β†’ 3x > 12 β†’ divide by 3 β†’ x > 4
Solve 2x + 5 ≀ 11: subtract 5 β†’ 2x ≀ 6 β†’ divide by 2 β†’ x ≀ 3

⚠️ THE FLIP RULE

When you multiply or divide both sides by a negative number, you must flip the inequality symbol.

Example: βˆ’2x < 8
Divide by βˆ’2: x > βˆ’4  (symbol flips from < to >!)
Example: βˆ’3x β‰₯ 15
Divide by βˆ’3: x ≀ βˆ’5  (symbol flips from β‰₯ to ≀!)
πŸ’‘ Think: if βˆ’1 < 3, multiply both sides by βˆ’1 β†’ 1 > βˆ’3 (the order reverses on the number line!)

Part 5: Integer Solutions & Word Problems

Sometimes we need integer (whole number) solutions only.

Find all integers satisfying βˆ’2 < x ≀ 5
x can be: βˆ’1, 0, 1, 2, 3, 4, 5
(βˆ’2 is excluded because it's strict <; 5 is included because of ≀)
Find all integers satisfying 1 ≀ x < 6
x can be: 1, 2, 3, 4, 5

Word Problems β†’ Inequalities:

"A bag must weigh more than 2 kg but no more than 10 kg." β†’ 2 < w ≀ 10
"You need at least 40 marks to pass." β†’ m β‰₯ 40
"The roller coaster requires riders to be under 130 cm." β†’ h < 130
πŸ’‘ Key words: more than β†’ > Β· less than β†’ < Β· at least / minimum β†’ β‰₯ Β· at most / maximum β†’ ≀

πŸ’‘ Worked Examples

Example 1: Equation vs Inequality β€” Side by Side

See how the approach is similar, but the solution is different!

βš–οΈ Equation: 2x + 3 = 11
Step 1: Subtract 3 from both sides
2x = 8
Step 2: Divide both sides by 2
x = 4
Solution: x = 4 (one value)
πŸ“ Inequality: 2x + 3 > 11
Step 1: Subtract 3 from both sides
2x > 8
Step 2: Divide both sides by 2
x > 4
Solution: x > 4 (infinite values: 5, 6, 7, …)
Key difference: an equation gives one answer; an inequality gives a range of answers.

Example 2: One-Step Inequality (with number line)

Solve x + 3 > 7 and show on a number line.

Step 1: Subtract 3 from both sides: x > 4
Solution: x > 4 β€” open circle at 4, arrow pointing right
0 1 2 3 4 5 6 7 8 9 x = 4 (open)

Example 3: Two-Step Inequality

Solve 3x βˆ’ 2 > 10

Step 1: Add 2 to both sides: 3x > 12
Step 2: Divide both sides by 3: x > 4
Solution: x > 4
Check: try x = 5 β†’ 3(5) βˆ’ 2 = 13 > 10 βœ“    try x = 3 β†’ 3(3) βˆ’ 2 = 7, not > 10 βœ—

Example 4: Negative Division β€” The Flip!

Solve βˆ’2x < 8

Step 1: Divide both sides by βˆ’2
⚠️ Dividing by βˆ’2 (a negative) β†’ flip the symbol: < becomes >
Step 2: x > βˆ’4
Solution: x > βˆ’4
Verify with x = 0: βˆ’2(0) = 0, and 0 < 8 βœ“   0 > βˆ’4 βœ“

πŸ“Š Interactive Number Line Plotter

Enter an inequality and watch it appear on the number line!

Examples: x > 3  Β·  x <= -1  Β·  x >= -2  Β·  x < 5



🍬 Integer Solution Clicker

Click all the integers that satisfy the inequality shown. Correct ones turn green, wrong ones flash red!

Loading…

Quick-plot these inequalities:

✏️ Exercise 1: Write the Inequality

Look at each number line and write the inequality it represents. Use <, >, ≀, or β‰₯.

✏️ Exercise 2: Draw the Inequality

For each inequality, choose the correct number line representation by clicking the right option.

✏️ Exercise 3: Solve One-Step Inequalities

Solve each inequality. Write your answer in the form x > a, x < a, x β‰₯ a, or x ≀ a (e.g. "x > 4").

✏️ Exercise 4: Two-Step Inequalities & The Flip Rule

Solve each inequality step by step. Watch for the flip rule when dividing by a negative!

⚠️ The Flip Rule β€” Step Builder

🚨 Dividing by a NEGATIVE β€” the symbol FLIPS! < β†’ >

✏️ Exercise 5: Integer Solutions & Word Problems

Part A: List the integers. Part B: Write an inequality for each word problem.

πŸ“ Practice Questions

πŸ† Challenge Questions

Harder problems β€” take your time and show your working!