"And" or "Or" Equations

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Examples, videos, and solutions to help Algebra I students learn how to describe the solution set of two equations (or inequalities) joined by either “and” or “or” and graph the solution set on the number line.

New York State Common Core Math Algebra I, Module 1, Lesson 15

Worksheets for Algebra I, Module 1, Lesson 15 (pdf)

Student Outcomes

Students describe the solution set of two equations (or inequalities) joined by either “and” or “or” and graph the solution set on the number line.

Lesson Summary

In mathematical sentences, like in English sentences, a compound sentence separated by

AND is true if both clauses are true
OR is true if at least one of the clauses is true

Exit Ticket

1.
a. Solve the system and graph the solution set on a number line.
x - 15 = 5 or 2x + 5 = 1.

b. Write a different system of equations that would have the same solution set.

2. Swimming pools must have a certain amount of chlorine content. The United States standard for safe levels of chlorine in swimming pools is at least 1 part per million and no greater than3 parts per million. Write a compound inequality for the acceptable range of chlorine levels.

3. Consider each of the following compound sentences:
x < 1 and x > -1
x < 1 or x > -1

Does the change of word from “and” to “or” change the solution set?
Use number-line graphs to support your answer.

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