Lesson 2.5 - Subtracting Integers

Five-Minute Check (over Lesson 2–4) Main Idea Key Concept: Subtract Integers Example 1:Subtract Positive Integers Example 2:Subtract Positive Integers Example 3:Subtract Negative Integers Example 4:Subtract Negative Integers Example 5:Evaluate an Expression Example 6:Use Integers to Solve a Problem

• Subtract integers.

Interactive Lab: Subtracting Positive and Negative Integers

Subtract Positive Integers Find 2 – 15. 2 – 15 = 2 + (–15) = –13

Answer: –13

To subtract 15, add –15. Simplify.

Find 13 – 21. A. –34 B. –8

A B C 0% D

0% D

A

D. 34

0% B

0%

1. 2. 3. 4.

C

C. 8

Subtract Positive Integers Find –13 – 8. –13 – 8 = –13 + (–8) = –21

Answer: –21

To subtract 8, add –8. Simplify.

Find –9 – 11. A. –20 B. –2

A B C 0% D

0% D

A

D. 20

0% B

0%

1. 2. 3. 4.

C

C. 2

Subtract Negative Integers Find 12 – (–6). 12 – (–6) = 12 + 6 = 18

Answer: 18

To subtract –6, add 6. Simplify.

Find 9 – (–4). A. –13 B. –5

A B C 0% D

0% D

A

D. 13

0% B

0%

1. 2. 3. 4.

C

C. 5

Subtract Negative Integers Find –21 – (–8).

–21 – (–8) = –21 + 8 = –13

Answer: –13

To subtract –8, add 8. Simplify.

Find 17 – (–6). A. –23 B. –11

A B C 0% D

0% D

A

D. 23

0% B

0%

1. 2. 3. 4.

C

C. 11

Evaluate an Expression ALGEBRA Evaluate g – h if g = –2 and h = –7.

g – h = –2 – (–7)

Answer: 5

Replace g with –2 and h with –7.

= –2 + 7

To subtract –7, add 7.

= 5

Simplify.

ALGEBRA Evaluate m – n if m = –6 and n = 4. A. –10 B. –2

A B C 0% D

0% D

A

D. 10

0% B

0%

1. 2. 3. 4.

C

C. 2

Use Integers to Solve a Problem GEOGRAPHY In Mongolia, the temperature can fall to –45ºC in January. The temperature in July may reach 40ºC. What is the difference between these two temperatures? To find the difference in temperatures, subtract the lower temperature from the higher temperature. 40 – (–45) = 40 + 45 = 85

To subtract –45, add 45. Simplify.

Answer: The difference between the temperatures is 85ºC.

TEMPERATURE On a particular day in Anchorage, Alaska, the high temperature was 15ºF and the low temperature was –11ºF. What is the difference between these two temperatures for that day? A. –26ºF B. –4ºF 1. 2. 3. 4.

C. 4ºF D. 26ºF

0% D

0% C

0% B

A

0%

A B C D

End of the Lesson

Pg 105, # 14-36 even, 37-43 all

Five-Minute Check (over Lesson 2–4) Image Bank Math Tools

Adding Integers Comparing and Ordering Integers Subtracting Positive and Negative Integers

(over Lesson 2-4)

Find –4 + 4. A. 8 B. 0

A B C 0% D

0% D

A

D. –8

0% B

0%

1. 2. 3. 4.

C

C. –4

(over Lesson 2-4)

Find 8 + (–7). A. –15 B. –1

A B C 0% D

0% D

A

D. 15

0% B

0%

1. 2. 3. 4.

C

C. 1

(over Lesson 2-4)

Find –3 + (–5). A. –8 B. –2

A B C 0% D

0% D

A

D. 8

0% B

0%

1. 2. 3. 4.

C

C. 2

(over Lesson 2-4)

Write an addition expression to describe the situation. Then find its sum. A bird flies up 50 feet and swoops back down 10 feet. A. –50 – (–10) = –60 B. –50 + 10 = –40

0% D

A B C 0%D C

A

D. 50 – (–10) = 60

0%

B

C. 50 – 10 = 40

1. 2. 3. 4. 0%

(over Lesson 2-4)

Write an addition expression to describe the situation. Then find its sum. Teresa dives 14 feet below the surface, then swims up 10 feet. A. –14 + 10 = 4 B. –14 + 10 = –4

D. 14 + 10 = 24

A B C D0% D

0%

C

0%

B

14 – 10 = 4 A

C

1. 2. 3. 4.0%

(over Lesson 2-4)

Evaluate x + y if x = –3 and y = –9. A. –12 B. –6 A B C 0% D

0% D

0% B

A

D. 12

0%

1. 2. 3. 4.

C

C. 6