Download Add and Subtract a Positive Number

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Add, subtract,
multiply, and divide with decimals; add with
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negative integers; subtract positive integers from negative
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integers; and verify the reasonableness of the results.
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UNDERLYING SKILLS AND CONCEPTS:
basic facts;
meaning of negative numbers
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Add and Subtract a Positive Number
You can use a number line to show positive and negative numbers.
When you add a positive number,
you look to the right and move forward.
To subtract a positive number,
you look to the left and move forward.
Subtract a
positive number:
go left.
Add a positive
number:
go this way.
subtract
add
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
1
Find !2 " 5.
Look at the number line. Start at !2. You need to add 5. Face right.
The second addend is positive, so move forward 5 spaces.
add 5
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
You end up at +3. So, !2 " 5 # 3.
E x am p l E
2
Find !1 ! 6.
On the number line, start at !1. You need to subtract 6. Face left.
The number you are subtracting is positive, so move forward 6 spaces.
subtract 6
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
You end up at !7. So, !1 ! 6 # !7.
page 76
Chapter 7 – Lesson 2
E – © CSL Associates, Inc. All rights reserved.
E x am p l E
The first number is
where you start from.
Name
P RAC T I C E
Add. You may use the number line.
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
1. 3 4
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
7
2. 3 4
1
3. 4 1
3
4. 7 3
4
5. 9 8
1
6. 1 3
2
7. 3 0
3
8. 3 2
1
9. 5 11
6
10. 8 15
7
11. 9 6
3
12. 10 9 1
Subtract. You may use the number line.
13. 3 4
1
14. 5 4
9
17. 8 8
0
18. 6 4
10
4
22. 7 2
9
21. 2 2
15. 7 6
1
16. 7 12
5
19. 1 8
9
20. 6 12
6
23. 10 17
7
24. 10 20 10
Write an equation and solve.
25. The temperature was 2°C. Then it rose 6 degrees.
What is the temperature now?
E – © CSL Associates, Inc. All rights reserved.
26. The temperature was 2°F. Then it fell 6 degrees.
What is the temperature now?
2 6 4°C
2 6 8°F
Circle the correct choice. Explain how you decided.
27. LaTara had a balance of $56 on her charge account. She paid off $30.
What is her balance now? Which equation can you use to solve the problem?
A
B
$56 $30 $86
$56 $30 $26
Math
Reasoning
C
D
$56 $30 $86
$56 $30 $26
Logical Reasoning
MR 3.3
28. Trisha said, “When you add a positive number to another number, you can never get a
result that is less than 0.” Sandi said, “You can get a result that is less than zero, but the
result is always greater than what you started with.”
Who is right? Explain your reasoning.
Sandi is right, Trisha is not. If you start with a negative number
and add a smaller positive number, you can get a negative result.
Chapter 7 – Lesson 2
page 77
MCX94.HW.CL.G5.FM&Lesson.v211
8/2/04
18:02
Page 52
Name
…at home!
P RAC T I C E
Add. You may use the number line.
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
1. 3 2
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
5
2. 3 2
1
3. 4 3
1
4. 3 3
0
5. 9 7
2
6. 1 6
5
7. 5 0
5
8. 3 9
6
9. 5 4
1
10. 8 12
4
11. 8 6
2
12. 10 7 3
Subtract. You may use the number line.
13. 3 2
1
14. 5 3
8
15. 8 6
2
16. 7 9
2
17. 8 9
1
18. 6 2
8
19. 1 5
6
20. 6 10
4
21. 4 4
8
22. 7 1
8
23. 10 12
2
24. 15 20
5
Write an equation and solve.
What is the temperature now?
26. The temperature was 5°F. Then it fell 8 degrees.
What is the temperature now?
5 8 3°C
5 8 13°F
Circle the correct choice. Explain how you decided.
27. Mia had a balance of $43 on her bank account. She paid off $25.
What is her balance now? Which equation can you use to solve the problem?
A
B
C
D
$43 $25 $68
$43 $25 $18
Math
Reasoning
$43 $25 $68
$43 $25 $18
Logical Reasoning
MR 3.3
28. Lynn said, “When you add a negative number to another number, you can never get a
result that is greater than 0.” Sandi said, “You can get a result that is greater than zero,
but the result is always less than what you started with.”
Who is right? Explain your reasoning.
Sandi is correct. If she starts with 2 and adds 4, she gets 2
which is less than 4. If she starts with 2 and adds any number,
she will have 2 less each time.
page 52
Home Resource and Homework
Chapter 7 Lesson 2
E – © CSL Associates, Inc. All rights reserved.
25. The temperature was 5°C. Then it rose 8 degrees.
MCX94TEG5CH01_32.v7.4.2 2/24/01 19:44 Page 143
Name
P RAC T I C E
Add. You may use the number line.
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
1. 3 4
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
7
2. 3 4
1
3. 4 1
3
4. 7 3
4
5. 9 8
1
6. 1 3
2
7. 3 0
3
8. 3 2
1
9. 5 11
6
10. 8 15
7
11. 9 6
3
12. 10 9 1
Subtract. You may use the number line.
13. 3 4
1
14. 5 4
9
17. 8 8
0
18. 6 4
10
4
22. 7 2
9
21. 2 2
15. 7 6
1
16. 7 12
5
19. 1 8
9
20. 6 12
6
23. 10 17
7
24. 10 20 10
Write an equation and solve.
25. The temperature was 2°C. Then it rose 6 degrees.
What is the temperature now?
E – © CSL Associates, Inc. All rights reserved.
26. The temperature was 2°F. Then it fell 6 degrees.
What is the temperature now?
2 6 4°C
2 6 8°F
Circle the correct choice. Explain how you decided.
27. LaTara had a balance of $56 on her charge account. She paid off $30.
What is her balance now? Which equation can you use to solve the problem?
A
B
C
D
$56 $30 $86
$56 $30 $26
Math
Reasoning
$56 $30 $86
$56 $30 $26
Logical Reasoning
MR 3.3
28. Trisha said, “When you add a positive number to another number, you can never get a
result that is less than 0.” Sandi said, “You can get a result that is less than zero, but the
result is always greater than what you started with.”
Who is right? Explain your reasoning.
Sandi is right, Trisha is not. If you start with a negative number
and add a smaller positive number, you can get a negative result.
Chapter 7 – Lesson 2
Student Book Page
page 77
Name
…at home!
P RAC T I C E
Add. You may use the number line.
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
1. 3 2
0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
5
2. 3 2
1
3. 4 3
1
4. 3 3
0
5. 9 7
2
6. 1 6
5
7. 5 0
5
8. 3 9
6
9. 5 4
1
10. 8 12
4
11. 8 6
2
12. 10 7 3
Subtract. You may use the number line.
13. 3 2
1
14. 5 3
8
15. 8 6
2
16. 7 9
2
17. 8 9
1
18. 6 2
8
19. 1 5
6
20. 6 10
4
21. 4 4
8
22. 7 1
8
23. 10 12
2
24. 15 20
5
Write an equation and solve.
What is the temperature now?
26. The temperature was 5°F. Then it fell 8 degrees.
What is the temperature now?
5 8 3°C
5 8 13°F
Circle the correct choice. Explain how you decided.
27. Mia had a balance of $43 on her bank account. She paid off $25.
What is her balance now? Which equation can you use to solve the problem?
A
B
C
D
$43 $25 $68
$43 $25 $18
Math
Reasoning
$43 $25 $68
$43 $25 $18
Logical Reasoning
MR 3.3
28. Lynn said, “When you add a negative number to another number, you can never get a
result that is greater than 0.” Sandi said, “You can get a result that is greater than zero,
but the result is always less than what you started with.”
Who is right? Explain your reasoning.
Sandi is correct. If she starts with 2 and adds 4, she gets 2
which is less than 4. If she starts with 2 and adds any number,
she will have 2 less each time.
page 52
Home Resource and Homework
Chapter 7 Lesson 2
E – © CSL Associates, Inc. All rights reserved.
25. The temperature was 5°C. Then it rose 8 degrees.