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2-1 Adding Integers
Warm Up
Problem of the Day
Lesson Presentation
Course 3
2-1 Adding Integers
Warm Up
Graph each number on a number line.
1. 5
2. 7
3. 4
4. 0
0
1
2
3
Add.
5. 22 + 19 41
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4
5
6
7
8
9 10
6. 17 + 18 35
2-1 Adding Integers
Problem of the Day
Start at (0, 0). Walk 3 blocks west and 2
blocks north. Then walk 4 blocks south
and 1 block east. What are your
coordinates?
(–2, –2)
Course 3
2-1 Adding Integers
Learn to add integers.
Course 3
2-1 Adding
Insert Lesson
Title Here
Integers
Vocabulary
integer
opposite
absolute value
Course 3
2-1 Adding Integers
Integers are sets of whole numbers,
including 0, and their opposites. The
sum of two opposite integers is zero.
–3 and 3 are opposites
-5 -4 -3 -2 -1
Negative integers
0
1
2
3
5
Positive integers
0 is its own opposite
Course 3
4
2-1 Adding Integers
Additional Example 1: Using a Number Line to Add
Integers
Use a number line to find the sum.
(–6) + 2
–6
2
–6 –5 –4 –3 –2 –1
0
1
2
3
4
5
You finish at –4, so (–6) + 2 = –4.
Helpful Hint
To add a positive number move to the right.
To add a negative number move to the left.
Course 3
2-1 Adding Integers
Try This: Example 1
Use a number line to find the sum.
(–3) + 7
–3
7
–6 –5 –4 –3 –2 –1
0
1
2
You finish at 4, so (–3) + 7 = 4.
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3
4
5
2-1 Adding Integers
Another way to add integers is to use
absolute value. The absolute value
of a number is its distance from 0. The
absolute value of –4, written as |–4|,
is 4; and the absolute value of 5 is 5.
Adding integers
If the signs are the same. . .
If the signs are different. . .
find the sum of the absolute
values. Use the same sign as
the integers.
find the difference of the
absolute values. Use the sign of
the integer with the larger
absolute value.
Course 3
2-1 Adding Integers
Additional Example 2A & 2B: Using Absolute Value
to Add Integers
Add.
A. 1 + (–2)
1 + (–2)
–1
Think: Find the difference of 2 and 1.
2 > 1; use the sign of 2.
B. (–8) + 5
(–8) + 5
–3
Course 3
Think: Find the difference of 8 and 5.
8 > 5; use the sign of 8.
2-1 Adding Integers
Additional Example 2C: Using Absolute Value to
Add Integers
Add.
C. (–2) + (–4)
Course 3
(–2) + (–4)
Think: Find the sum of 2 and 4.
–6
Same sign; use the sign of the
integers.
2-1 Adding Integers
Try This: Example 2A & 2B
Add.
A. 3 + (–6)
3 + (–6)
–3
Think: Find the difference of 6 and 3.
6 > 3; use the sign of 6.
B. (–4) + 1
(–4) + 1
–3
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Think: Find the difference of 4 and 1.
4 > 1; use the sign of 4.
2-1 Adding Integers
Try This: Example 2C
Add.
C. (–6) + (–7)
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(–6) + (–7)
Think: Find the sum of 6 and 7.
–13
Same sign; use the sign of the
integers.
2-1 Adding Integers
Additional Example 3: Evaluating Expressions with
Integers
Evaluate c + 4 for c = –8.
c+4
(–8) + 4
Replace c with –8.
Think: Find the difference of 8 and 4.
–8 + 4 = –4 8 > 4; use the sign of 8.
Course 3
2-1 Adding Integers
Try This: Example 3
Evaluate d + 7 for d = –3.
d+7
(–3) + 7
Replace d with –3.
Think: Find the difference of 7 and 3.
–3 + 7 = 4
7 > 3; use the sign of 7.
Course 3
2-1 Adding Integers
Additional Example 4: Application
Katrina opened a new bank account. Find her
account balance after the first four transactions
listed below.
Deposits: $200, $20 Withdrawals: $166, $38
200 + 20 + (–166) + (–38)
(200 + 20) + (–166 + –38)
220 + (–204)
Use a positive sign for
deposits and a negative
sign for withdrawals.
Group integers with
same signs.
Add integers within each
group.
220 > 204; use the sign
of 220.
Katrina’s account balance after the first four transactions is $16.
16
Course 3
2-1 Adding Integers
Try This: Example 4
Michael opened a new bank account. Find his account
balance after the first four transactions listed below.
Deposits: $175, $95
Withdrawals: $133, $65
175 + 95 + (–133) + (–65)
(175 + 95) + (–133 + –65)
270 + (–198)
72
Use a positive sign for
deposits and a negative
sign for withdrawals.
Group integers with
same signs.
Add integers within each
group.
270 > 198; use the sign
of 270.
Michael’s account balance after the first four transactions is $72.
Course 3
2-1 Adding
Integers
Insert Lesson
Title Here
Lesson Quiz: Part 1
Add.
1. –7 + (– 7)
–14
2. 15 + (–9) + (–2)
4
Evaluate each expression for the given value
of the variable.
3. 13 + r for r = –15
–2
4. 2 + b + (–9) for b = –6
–13
Course 3
2-1 Adding
Integers
Insert Lesson
Title Here
Lesson Quiz: Part 2
5. On Monday, a local dog shelter had six dogs.
By Friday they had found homes for three, but
took in two more. Then how many dogs were
in the shelter? 5 dogs
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