Lesson 2.4 - Adding Integers

Five-Minute Check (over Lesson 2–3) Main Idea and Vocabulary Example 1:Add Integers with the Same Sign Key Concept:Add Integers with the Same Sign Example 2:Add Integers with the Same Sign Key Concept:Additive Inverse Property Example 3:Add Integers with Different Signs Example 4:Add Integers with Different Signs Key Concept:Add Integers with Different Signs Example 5:Add Integers with Different Signs Example 6:Add Integers with Different Signs Example 7:Use the Additive Inverse Property Example 8:Use Integers to Solve a Problem

• Add integers.

• opposites • additive inverse

Add Integers with the Same Sign Find –6 + (–3). Use a number line. Start at 0. Move 6 units left to show –6. From there, move 3 units left to show –3.

Answer: So, –6 + (–3) = –9.

Find –5 + (–2). A. –7 B. –3 C. 3 0% D

A B C 0% D C

A

0% B

0%

D. 7

1. 2. 3. 4.

Add Integers with the Same Sign Find –34 + (–21). –34 + (–21) = –55

Answer: –55

Both integers are negative, so the sum is negative.

Find –27 + (–19). A. –46 B. –8

A B C 0% D

0% D

A

D. 46

0% B

0%

1. 2. 3. 4.

C

C. 8

Add Integers with Different Signs Find 8 + (–7). Use a number line. Start at zero. Move 8 units right. Then move 7 units left.

Answer: So, 8 + (–7) = 1.

Find 6 + (–2). A. –8 B. –4 C. 4 0% D

A B C 0% D C

A

0% B

0%

D. 12

1. 2. 3. 4.

Add Integers with Different Signs Find –5 + 4.

Use a number line. Start at 0. Move 5 units left. Then move 4 units right.

Answer: So, –5 + 4 = –1.

Find –3 + 5. A. –8 B. 2 C. 8 0% D

A B C 0% D C

A

0% B

0%

D. 15

1. 2. 3. 4.

Add Integers with Different Signs Find 2 + (–7).

2 + (–7) = –5

Answer: –5

Subtract absolute values; 7 – 2 = 5. Since –7 has the greater absolute value, the sum is negative.

Find 5 + (–9). A. –14 B. –4

A B C 0% D

0% D

A

D. 14

0% B

0%

1. 2. 3. 4.

C

C. 4

Add Integers with Different Signs Find –9 + 6.

–9 + 6 = –3

Answer: –3

Subtract absolute values; 9 – 6 = 3. Since –9 has the greater absolute value, the sum is negative.

Find 7 + (–3). A. –10 B. –4

A B C 0% D

0% D

A

D. 10

0% B

0%

1. 2. 3. 4.

C

C. 4

Use the Additive Inverse Property Find 11 + (–4) + (–11).

11 + (–4) + (–11) = 11 + (–11) + (–4)

Answer: –4

Commutative Property (+)

= 0 + (–4)

Additive Inverse Property

= –4

Identity Property of Addition

Find 5 + (–11) + (–5). A. –21 B. –11

A B C 0% D

0% D

A

D. 16

0% B

0%

1. 2. 3. 4.

C

C. 6

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.

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

1. 2. 3. 4.

C. 12 + (–9); 3 0% D

0% C

0% B

D. 12 + 9; 21

A

0%

A B C D

End of the Lesson

Pg 98-99, # 1-6 all, 10-42 even.

Five-Minute Check (over Lesson 2–3) Image Bank Math Tools

Adding Integers Comparing and Ordering Integers Subtracting Positive and Negative Integers

(over Lesson 2-3)

Name the ordered pair for the point C. Then identify the quadrant in which the point C lies. A. (3, 3), I

B. (3, –3), II 1. 2. 3. 4.

C. (3, 3), III 0%

0% D

0%

C

A

0%

B

D. (3, –3), IV

A B C D

(over Lesson 2-3)

Name the ordered pair for the point L. Then identify the quadrant in which the point L lies. A. (–3, 2), III B. (2, –3), I 1. 2. 3. 4.

C. (2, –3), II 0% D

0% C

A

D. (–3, 2), II

0% B

0%

A B C D

(over Lesson 2-3)

Name the ordered pair for the point S. Then identify the quadrant in which the point S lies. A. (3, –3), I B. (3, –3), IV 1. 2. 3. 4.

C. (–3, 3), I 0%

0% D

0%

C

A

0%

B

D. (–3, 3), IV

A B C D

(over Lesson 2-3)

Which choice shows the graph of the point W(4, –2)?

0%

0%

1. 2. 3. 4.

A B C 0% D

0% D

D.

C

C.

B

B.

A

A.

(over Lesson 2-3)

Which choice shows the graph of the point N(–3, 0)?

0%

0%

1. 2. 3. 4.

A B C 0% D

0% D

D.

C

C.

B

B.

A

A.

(over Lesson 2-3)

Which ordered pair is 5 units left and 3 units up from the origin? A. (–5, –3) B. (5, –3)

0% D

0% B

D. (–5, 3)

A

0%

A B C 0% D C

C. (5, 3)

1. 2. 3. 4.