Use with Ready Instruction Lesson 2
Dear Family,
Your child is learning to understand how to
subtract positive and negative integers.
Addition and subtraction are inverse operations. You can write any
subtraction problem as an addition problem. Here’s an example:
Subtraction problem:
7
2354
Addition problem:
7
1(23)
same result
54
Keep the same first number.Use the opposite of
the second number.
Use the inverse operation.
This means that if you know how to add positive and negative integers,
you know how to subtract them.
23
21
0
1
2
3
4
5
6
7
8
9
10
Consider the following example:
The temperature is 21°F at noon. In
the evening, the temperature is 23°F.
What is the difference in the
temperatures?
30
30
20
20
Noon
10
0
Evening
210
F
0
220
210
220
10
210
220
210
230
C
220
F
230
C
On the next page you will see a way your child may find the
difference in the temperatures.
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Lesson 2 Understand Subtraction of Positive and Negative Integers
9
Understand Subtraction of Positive and Negative
Integers: Sample Solution
The temperature is 21°F at noon. In the evening, the temperature
is 23°F. What is the difference in the temperatures?
Write a subtraction problem and use a number line to model an
equivalent addition problem.
To do this, keep the first number the same, change subtraction to
addition, and add the opposite of the second number. You can do this
because subtracting a number is the same as adding its opposite.
21 2 (23) 5 21 1 3
Now you can use a number line to find the sum.
13
25 24 23 22 21
0
1
2
3
4
5
Solve the addition problem: 21 1 3 5 2.
Answer: The result is 2, meaning that the difference between the
temperature of 21°F at noon and 23°F in the evening is 2°F.
10
Lesson 2 Understand Subtraction of Positive and Negative Integers
©Curriculum Associates, LLC Copying is not permitted.