Flipping the inequality when dividing by a negative number
Integer solutions: list all integers satisfying β2 < x β€ 5
Writing inequalities from word problems
π Learn: Inequalities
Part 1: Inequality Symbols
An inequality compares two values and tells us one is bigger, smaller, or equal to the other.
Symbol
Meaning
Example
Read as
<
Less than
x < 5
"x is less than 5"
>
Greater than
x > β2
"x is greater than β2"
β€
Less than or equal to
x β€ 8
"x is at most 8"
β₯
Greater than or equal to
x β₯ 0
"x is at least 0"
π‘ 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 β the value is included (β€ or β₯)
The arrow points in the direction of all values that satisfy the inequality
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 β€ 10: divide both sides by 2 β x β€ 5
Solve x β 4 β₯ β1: add 4 to both sides β x β₯ 3
π‘ 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 β 2 > 10: add 2 β 3x > 12 β divide by 3 β x > 4
Solve 2x + 5 β€ 11: subtract 5 β 2x β€ 6 β divide by 2 β x β€ 3
β οΈ THE FLIP RULE
When you multiply or divide both sides by a negative number, you must flip the inequality symbol.
Example: β2x < 8 Divide by β2: x > β4 (symbol flips from < to >!)
Example: β3x β₯ 15 Divide by β3: x β€ β5 (symbol flips from β₯ to β€!)
π‘ Think: if β1 < 3, multiply both sides by β1 β 1 > β3 (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 β2 < x β€ 5 x can be: β1, 0, 1, 2, 3, 4, 5 (β2 is excluded because it's strict <; 5 is included because of β€)
Find all integers satisfying 1 β€ 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 β€ 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
π‘ Key words: more than β > Β· less than β < Β· at least / minimum β β₯ Β· at most / maximum β β€
π‘ Worked Examples
Example 1: Equation vs Inequality β Side by Side
See how the approach is similar, but the solution is different!
βοΈ 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)
π 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, β¦)
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
Example 3: Two-Step Inequality
Solve 3x β 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) β 2 = 13 > 10 β try x = 3 β 3(3) β 2 = 7, not > 10 β
Example 4: Negative Division β The Flip!
Solve β2x < 8
Step 1: Divide both sides by β2
β οΈ Dividing by β2 (a negative) β flip the symbol: < becomes >
Step 2: x > β4
Solution: x > β4
Verify with x = 0: β2(0) = 0, and 0 < 8 β 0 > β4 β
π 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
π¬ Integer Solution Clicker
Click all the integers that satisfy the inequality shown. Correct ones turn green, wrong ones flash red!
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Quick-plot these inequalities:
βοΈ Exercise 1: Write the Inequality
Look at each number line and write the inequality it represents. Use <, >, β€, or β₯.
βοΈ Exercise 2: Draw the Inequality
For each inequality, choose the correct number line representation by clicking the right option.
βοΈ Exercise 3: Solve One-Step Inequalities
Solve each inequality. Write your answer in the form x > a, x < a, x β₯ a, or x β€ a (e.g. "x > 4").
βοΈ Exercise 4: Two-Step Inequalities & The Flip Rule
Solve each inequality step by step. Watch for the flip rule when dividing by a negative!
β οΈ The Flip Rule β Step Builder
π¨ Dividing by a NEGATIVE β the symbol FLIPS! < β >
βοΈ Exercise 5: Integer Solutions & Word Problems
Part A: List the integers. Part B: Write an inequality for each word problem.
π Practice Questions
π Challenge Questions
Harder problems β take your time and show your working!