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Add Integers with the Same Sign
Find –6 + (–3).
Use a number line.
Answer: So, –6 + (–3) = –9.
From there, move 3 units left to show –3.
Move 6 units left to show –6.
Start at 0.
1. A
2. B
3. C
4. D
A. –7
B. –3
C. 3
D. 7
Find –5 + (–2).
Add Integers with the Same Sign
Find –34 + (–21).
–34 + (–21) = –55 Both integers are negative, so the sum is negative.
Answer: –55
1. A
2. B
3. C
4. D
A. –46
B. –8
C. 8
D. 46
Find –27 + (–19).
Add Integers with Different Signs
Find 8 + (–7).
Answer: So, 8 + (–7) = 1.
Use a number line.
Then move 7 units left.
Move 8 units right.
Start at zero.
1. A
2. B
3. C
4. D
A. –8
B. –4
C. 4
D. 12
Find 6 + (–2).
Find –5 + 4.
Answer: So, –5 + 4 = –1.
Add Integers with Different Signs
Use a number line.
Then move 4 units right.
Move 5 units left.
Start at 0.
1. A
2. B
3. C
4. D
A. –8
B. 2
C. 8
D. 15
Find –3 + 5.
Find 2 + (–7).
Answer: –5
Add Integers with Different Signs
2 + (–7) = –5 Subtract absolute values;
7 – 2 = 5. Since –7 has the greater absolute
value, the sum is negative.
1. A
2. B
3. C
4. D
A. –14
B. –4
C. 4
D. 14
Find 5 + (–9).
Find –9 + 6.
Answer: –3
Add Integers with Different Signs
–9 + 6 = –3 Subtract absolute values;
9 – 6 = 3. Since –9 has the greater absolute value, the sum is negative.
1. A
2. B
3. C
4. D
A. –10
B. –4
C. 4
D. 10
Find 7 + (–3).
Find 11 + (–4) + (–11).
Answer: –4
Use the Additive Inverse Property
11 + (–4) + (–11) = 11 + (–11) + (–4) Commutative Property
(+)
= 0 + (–4) Additive Inverse Property
= –4 Identity Property of Addition
1. A
2. B
3. C
4. D
A. –21
B. –11
C. 6
D. 16
Find 5 + (–11) + (–5).
Use Integers to Solve a Problem
OCEANOGRAPHY Oceanographers divide the ocean into three light zones. The deeper the water, the less light shines through. The middle zone is called the Twilight Zone. The lowest part of this zone is 1,000 meters below the surface of the water. The top of this zone lies 800 meters above the lowest zone. What is the depth of the top of the zone? Write an addition sentence to describe this situation. Then find the sum and explain its meaning.
–1,000 + 800 = –200
Answer: The depth of the top of the middle zone is 200 meters below the surface of the water.
1. A
2. B
3. C
4. D
During an hour trading baseball cards with his friends, Kyle increases the size of his collection by 12 cards and then loses nine cards. Write an addition sentence to describe this situation. Then find its sum.
A. –12 + (–9); –21
B. –12 + 9; –3
C. 12 + (–9); 3
D. 12 + 9; 21
End of the Lesson
