Teaching Notes 1.16: Subtracting Integers
Subtraction of integers can be easy for students to master if they remember to rewrite the
subtraction problem as an addition problem and then add the integers. Unfortunately, forgetting
to rewrite the problem is a very common mistake.- Explain to your students that subtracting a number is defined by adding its opposite.
a−b=a+(−b), ifaandbare integers. - Explain that any subtraction problem can be rewritten as an addition problem. It is often
easier to add integers than subtract them. - Review the information and examples on the worksheet with your students. Encourage them
to rewrite subtraction problems involving integers by following the steps provided. If neces-
sary, review the steps for adding integers provided with 1.15: ‘‘Adding Integers with Differ-
ent Signs.’’
EXTRA HELP:
The opposite of a negative number is a positive number and the opposite of a positive number is a
negative number.ANSWER KEY:
(1)− 7 (2)− 9 (3) 15 (4) 28 (5) 16 (6)− 5 (7)− 15 (8) 0 (9)− 11 (10) 35 (11)− 14 (12)− 2
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(Challenge)Rewrite the problem as− 3 −[− 10 +(−6)]. Find the sum of−10 and−6, which is
−16. Rewrite the subtraction problem as addition:− 3 −(−16)=− 3 +16. The sum is 13.
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