Mathematics
Grade 7
15 min
Write inequalities from number lines
Write inequalities from number lines
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1
Introduction & Learning Objectives
Learning Objectives
Identify the key components of an inequality represented on a number line (circle type, shading direction, and value).
Distinguish between strict inequalities (<, >) and inclusive inequalities (≤, ≥) based on open and closed circles.
Correctly determine the direction of the inequality symbol based on the shaded region of the number line.
Write a one-variable inequality that accurately represents a given number line graph.
Interpret number lines with different scales and use the correct numerical value in their inequalities.
Write compound inequalities for number lines showing a segment between two points.
Ever wondered how to describe a range of possibilities, like 'temperatures above 0°C' or 'ages 13 and older' using math? 🌡️ Nu...
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Key Concepts & Vocabulary
TermDefinitionExample
InequalityA mathematical statement that compares two expressions using an inequality symbol (like <, >, ≤, or ≥), showing that one quantity is not necessarily equal to another.$$x > 5$$ (x is greater than 5)
Number LineA visual representation of numbers as points on a straight line, ordered from least to greatest, used to graph inequalities.A line with integers marked, and a specific point or region highlighted.
Open Circle (or Unfilled Circle)A circle on a number line that is not filled in, indicating that the endpoint number is NOT included in the solution set of the inequality.An open circle at 3 means the solution is all numbers *close to* 3 but not including 3 itself, like 3.0001 or 2.999.
Closed Circle (or Filled Circle)A circle on a number line that i...
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Core Formulas
Rule for Open Circles
An open circle on a number line corresponds to a strict inequality symbol: less than ($$<$ $) or greater than ($$>$ $).
If the endpoint is not included in the solution, use < or >. For example, an open circle at 'a' shaded right means $$x > a$$, and shaded left means $$x < a$$.
Rule for Closed Circles
A closed circle on a number line corresponds to an inclusive inequality symbol: less than or equal to ($$\le$$) or greater than or equal to ($$\ge$$).
If the endpoint is included in the solution, use ≤ or ≥. For example, a closed circle at 'a' shaded right means $$x \ge a$$, and shaded left means $$x \le a$$.
Rule for Shading Direction
The direction of the shaded region indicates the direction of the inequality....
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Challenging
A number line shows an open circle at -3. The line is shaded to the right. Which of the following inequalities does NOT represent the number line?
A.x > -3
B.-3 < x
C.x ≥ -3
D.The set of all real numbers strictly greater than -3
Challenging
The acceptable weight (w) in kilograms for a package is at least 1.5 kg and less than 10 kg. Which inequality represents the number line for this situation?
A.1.5 < w < 10
B.1.5 ≤ w < 10
C.1.5 ≤ w ≤ 10
D.1.5 < w ≤ 10
Challenging
A number line is marked in increments of 0.2. The shaded region is between a closed circle at -0.8 and an open circle at 0.2. Which inequality represents this graph?
A.-0.8 ≤ x < 0.2
B.-0.8 < x ≤ 0.2
C.x ≥ -0.8 and x < 0.2
D.Both A and C are correct
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