Math Lesson Plan · Grades 5–8

Subtracting Positive and Negative Numbers Lesson

Teach students to subtract positive and negative integers with this six-page lesson plan and worksheet. The central rule: rewrite any subtraction as addition by changing the sign of the subtracted number. Students practice 29 problems covering standard subtraction, three-term expressions, and comparing results. Full answer key included.

Lesson Overview

Subtracting Positive and Negative Numbers

Subtracting integers follows one key rule: change the subtraction sign to addition and flip the sign of the number being subtracted. For example, 5 − (−3) becomes 5 + 3 = 8, because subtracting a negative is the same as adding a positive. And 4 − 9 becomes 4 + (−9) = −5.

The lesson works through this rule with multiple examples, reminding students to use the absolute value concepts from Lesson 1 to determine the sign of the result. Once the subtraction is rewritten as addition, the same gain/loss reasoning from Lesson 2 applies.

The worksheet has 29 problems: standard two-number subtraction problems, three-term expressions, and comparison problems where students subtract both sides and compare the results. Complete answer key is on page 6.

How to Use This Lesson

1. Review integer addition from the previous lesson. Present the subtraction rule on pages 1–3: every subtraction becomes addition with the opposite sign.

2. Work through several board examples with students, emphasizing that the rule works the same regardless of whether the original numbers are positive or negative.

3. Distribute the worksheet. Complete all 29 problems, then review using the answer key on page 6.

Printable Resource

A classroom-ready PDF with everything in one printable resource.

Keep Exploring Math