Teaching Notes 3.11: Writing Inequalities
Writing inequalities involves using the same skillsas writing equations, except that students
must translate key words that transform a comparison into a number sentence. This often proves
to be a problem for some students.- Explain to your students that just as they used expressions to write equations, they will use
expressions to write inequalities. Depending on their abilities, you may wish to review 1.7:
‘‘Writing Expressions.’’ - Explain that equations indicate that two expressions are equal. Inequalities indicate that
two expressions are unequal. An expression may be greater than, greater than or equal to,
less than, or less than or equal to another expression. - Review the information and the examples on the worksheet with your students. Explain that
inequality symbols are used to compare two quantities or expressions and that inequality
symbols can be used to complete a number sentence when the quantities on each side of the
number sentence are not equal. - Provide real-life situations where the inequality symbols are used. For example, a bus
can hold at most 48 people. Ifnrepresents the number of people planning to take a bus,
n≤48 models the situation. Likewise, if at least 20 students are needed to form a club,
n≥20 models this situation.
EXTRA HELP:
Inequalities are number sentences and always contain an inequality symbol.ANSWER KEY:
(1) 5 < 10 (2)− 2 >− 4 (3) 3 ≥ 0 (4)n− 2 ≤ 16 (5) 4 n≥ 15
(6)n+(−2)≥ 5 (7)
n
5
≤ 21 (8) 5 n> 90 (9)n>90 percent (10)n≥ 300
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(Challenge)‘‘7 less than a number’’ is an expression that can be written asn−7. ‘‘7 is less than
a number’’ is an inequality that can be written as 7<n.
------------------------------------------------------------------------------------------108 THE ALGEBRA TEACHER’S GUIDE