MS After School Intervention
Unit: Operations with Integers
Day 2 Lesson
Objective
Students will subtract integers.
Common Core Standards:
7.NS.1 Apply and extend previous understandings of addition and subtraction to add
and subtract rational numbers; represent addition and subtraction on a horizontal
or vertical number line diagram.
7.NS.1a Describe situations in which opposite quantities combine to make 0. For
example, a hydrogen atom has 0 charge because its two constituents are oppositely
charged.
7.NS.1b Understand p + q as the number located a distance q from p, in the positive
or negative direction depending on whether q is positive or negative. Show that a
number and its opposite have a sum of 0 (are additive inverses). Interpret sums of
rational numbers by describing real-world contexts.
7.NS.1c Understand subtraction of rational numbers as adding the additive inverse,
p  q  p  (q) . Show that the distance between two rational numbers on the
number line is the absolute value of their difference, and apply this principle in realworld contexts.
7.NS.1d Apply properties of operations as strategies to add and subtract rational
numbers.
Materials
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Chart paper
Whiteboards or sheet protectors with paper
Pencils
Sentence or paper strips
Teaching Student-Centered Mathematics 5-8
“Day 2 Number Lines” resource sheet
“Day 2: Four Corners Problems” resource sheet
“Day 2: Ready! Set! Go!” resource sheet
Scenario of the Day (10 min)
Have students think back to adding integers. What happens when you add 2 positive
numbers? (Response: You add the numbers and the answer will be positive) What
happens when you add 2 negative numbers? (Response: You add the numbers and the
answer is negative) What do you do when you add different signs? (Response: You
subtract the numbers and the answer has the sign of the higher number)
What do you think we should do to subtract integers? (Possible answers: “Subtract and
take the sign of the higher value”, “just subtract”, “keep-change-change,” “add the
opposite,” etc) Make a list of the suggestions named on chart paper or chalkboard. You
will refer back to this list during the lesson.
Pose this question: “Jake borrowed $5 from his mom. He paid her back $2. What is his
financial status now? Justify your answer.”
How would this question look as a math problem? –5 – (–2)
Introductory Activity (20 minutes)
Students will use arrows and number lines to model subtraction of integers. Each student
needs paper (maybe use colored paper) or a white board and a pencil. Refer to pages 143
and 144 in the Teaching Student-Centered Mathematics 5-8. The arrow and number line
model views subtraction as “back up” or “move in the opposite direction.”
Start with 5 – 2. Students will draw an arrow from 0 to 5. To show – 2 an arrow will be
drawn from the 5 to the 2 in the negative direction. Students should be at 3 on the
number line.
Now try –5 – 2. Students will draw an arrow from 0 to –5. Then they will show – 2 by
drawing an arrow from the –5 to the 2 in the negative direction. Students should arrive at
–7 on the number line.
Do –5 – (–2). Students will again draw an arrow from 0 to –5. Then students will draw
an arrow from the –5 to the 2 in the positive direction. Students should arrive at –3 on
the number line.
Have students complete additional subtraction problems on the number line.
Four Corners (15 minutes)
Students will practice solving integer subtraction problems with a partner and use four
corners to stand with like-minded peers. Pairs can use paper or white boards. Students
may or may not want to use their arrow/number line models. Discussions should take
place at each of the corners (A, B, C, and D).
Teachers should have the corners labeled A, B, C, and D. Using the questions on the
resource sheet, make a key for the overhead/document camera for students to report to
the correct corner after each question. Pose one question at a time, giving time for
students to work with their partners. Then show 4 answer choices and have students go
to the corner that corresponds with their answer choice. Allow time for discussion at the
corners, and possibly allow groups to select a new corner, if need be.
(Answers: 1. B 2. C 3. A 4. C 5. C 6. D)
Ready-Set-Go! (20 minutes)
Before class begins, print each “Ready Set Go!” problem set on different colors of paper
and cut the problems into strips. Divide the class into groups of three. Each group will be
assigned a different color. Each group will solve the same five questions. Give each
group a different strip to solve. As a group finishes, a runner from the group should bring
the problem to the teacher to be checked. If the answer is correct, give the runner a new
question. If the answer is incorrect, the group must correct the solution. Play continues
until a group has correctly finished all the sentence strips. You can keep score by giving
three points to the group that finishes the question first and two points to the group that
finishes the question second, and one point to the group that finishes the question third.
Each “round” allows for different groups to gather points.
Solutions:
–12 – 9 = –21
3 – (–24) = 27
–13 – (–2) = –11
19 – (–7) = 26
–17 – (–17) = 0
Solving the Scenario (15 minutes)
Go back to the list of suggestions made at the beginning of the lesson. Ask students to
share their thoughts about the ideas presented. Ask students to make a conclusion about a
rule that could be used for subtracting integers. (Note: Lead students to arrive at “adding
the opposite.” “Keep, change, change” should be discouraged.)
3-2-1 Closure (10 minutes)
Have students write down 3 positives about the day, 2 ideas they learned, and 1 question
they may have.
Call on a few students to share responses. Collect responses to gather information about
student understanding.
Day 2 Number Lines
Day 2: Four Corners Problems
Problem 1: 4 – 7
A. –11
B. –3
C. 3
D. 11
Problem 2: –8 + 10
A. –18
B. –2
C. 2
D. 18
Problem 3: –2 – 7
A. –9
B. –5
C. 5
D. 9
Problem 4: –2 + 6
A. –8
B. –4
C. 4
D. 8
Problem 5: –11 – (–12)
A. –23
B. –1
C. 1
D. 23
Problem 6: 3 – (–14)
A. –17
B. –11
C. 11
D. 17
Day 2: Ready! Set! Go!
–12 – 9
3 – (–24)
–13 – (–2)
19 – (–7)
–17 – (–17)