Mathematics
Grade 6
15 min
Solve inequalities using addition and subtraction (Advanced)
Solve inequalities using addition and subtraction (Advanced)
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1
Introduction & Learning Objectives
Learning Objectives
Identify and interpret inequality symbols (<, >, ≤, ≥).
Understand that an inequality has a set of solutions, not just one.
Solve one-variable inequalities involving positive and negative integers using the Addition Property of Inequality.
Solve one-variable inequalities involving positive and negative integers using the Subtraction Property of Inequality.
Graph the solution sets of inequalities on a number line, correctly using open and closed circles.
Translate simple real-world scenarios into one-variable inequalities.
Ever wonder how many cookies you can eat without going over your daily sugar limit? 🍪 Or how many minutes you can play a game without missing your bedtime? These are all about inequalities!
In this lesson, you'll learn how t...
2
Key Concepts & Vocabulary
TermDefinitionExample
InequalityA mathematical statement that compares two expressions using an inequality symbol (<, >, ≤, ≥).x + 3 < 10
Solution to an InequalityAny value of the variable that makes the inequality true. Unlike equations, inequalities often have many solutions.For x < 7, numbers like 6, 5, 0, -10 are all solutions.
Addition Property of InequalityAdding the same number to both sides of an inequality does not change the truth of the inequality.If x - 5 > 2, then x - 5 + 5 > 2 + 5, which means x > 7.
Subtraction Property of InequalitySubtracting the same number from both sides of an inequality does not change the truth of the inequality.If x + 4 ≤ 9, then x + 4 - 4 ≤ 9 - 4, which means x ≤ 5.
Number LineA line on which numbers are marked at regular inter...
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Core Formulas
Addition Property of Inequality
If $a < b$, then $a + c < b + c$. This also applies to $>, \le, \ge$.
To isolate a variable that is being subtracted, add the same number to both sides of the inequality.
Subtraction Property of Inequality
If $a < b$, then $a - c < b - c$. This also applies to $>, \le, \ge$.
To isolate a variable that is being added, subtract the same number from both sides of the inequality.
Graphing Solutions on a Number Line
For $<$ or $>$, use an **open circle** on the number representing the boundary. For $\le$ or $\ge$, use a **closed circle** on the number representing the boundary. Draw an arrow pointing in the direction of the solution set (left for less than, right for greater than).
This rule helps visualize all possi...
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Challenging
The solution to an inequality is graphed with a closed circle on the integer 5 and an arrow pointing to the left. If the original inequality was `x - c ≤ -2`, what is the value of `c`?
A.-7
B.3
C.7
D.-3
Challenging
If `a - b < c` and `b` is a positive integer, which of the following statements MUST be true?
A.a < c
B.a > c
C.a < c + b
D.a > c + b
Challenging
A number `p` is an integer that satisfies the inequality `p - 12 ≥ -8`. What is the smallest possible value of `p`?
A.-4
B.5
C.4
D.-20
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