Download Adding Integers

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Adding Integers
BEFORE
Now
WHY?
You added whole numbers,
fractions, and decimals.
You’ll add integers.
So you can find the change in stock
value, as in Ex. 34.
In the Real World
10 G
20
30
40
50
1
40
EXAMPLE
30
absolute value, p. 539
20
Football During a high
school football game, your
team gained 6 yards on
the first play, lost
8 yards on the second
play, and gained 11 yards
on the third play. Did your
team gain the 10 yards
needed for a first down?
G 10
Word Watch
G 10
20
30
40
50
40
30
20
10 G
Modeling Integer Addition
To understand the problem above, read and organize the information.
First play:
6 means a gain of 6 yards.
Second play:
8 means a loss of 8 yards.
Third play:
11 means a gain of 11 yards.
Start at 0 on a number line. Use arrows to represent gains and losses.
Move right to add a positive number and left to add a negative number.
11
8
6
3 2 1
0
1
2
First play:
066
Second play:
6 (8) 2
Third play:
2 11 9
3
4
5
6
7
8
9
10
ANSWER Your team gained only 9 yards during the three plays,
which was not enough for a first down.
Your turn now
1. 4 (4)
538
Chapter 11
Integers
Find the sum using a number line.
2. 6 6
3. 8 10
4. 5 (9)
Page 2 of 4
Absolute Value The absolute value of a number is its distance from
0 on a number line. The absolute value of a number a is written a.
3 units
3
2
3 units
1
0
1
2
The absolute value of 3 is 3
and the absolute value of 3 is 3.
3
3 3 3
You can use absolute value to add integers.
Adding Integers
Words
Numbers
Same Signs To add two integers with
the same sign, add their absolute values
and write their common sign.
358
Different Signs To add two integers
with different signs, first subtract the
lesser absolute value from the greater
absolute value. Then write the sign of the
number with the greater absolute value.
EXAMPLE
with
Solving
When you find the sum of
two numbers with different
signs, you first find the
number with the greater
absolute value.
2
3 (5) 8
7 10 3
7 (10) 3
Adding Integers
a. In the sum 4 (7), both numbers have a negative sign. To find
the sum, find 4 7 and write a negative sign.
4 (7) 11
b. In the sum 8 3, the numbers have different signs and 8 has the
greater absolute value. To find the sum, find 8 3 and write a
negative sign.
8 3 5
c. In the sum 6 9, the numbers have different signs and 9 has the
greater absolute value. To find the sum, find 9 6.
6 9 3
Your turn now
Find the absolute value of each number in the
expression. Then find the sum.
5. 10 (5)
6. 9 (2)
7. 8 (15)
Lesson 11.2
8. 25 (25)
Adding Integers
539
Page 3 of 4
INTERNET
Exercises
eWorkbook Plus
CLASSZONE.COM
More Practice, p. 718
Getting Ready to Practice
Vocabulary Find the absolute value of the number.
1. 5
2. 8
3. 7
4. 0
6. 3 (6)
7. 7 (1)
8. 2 (8)
Find the sum.
5. 5 (4)
9. Find the Error Describe and correct the error in the solution.
1 5 5
–3 –2 –1
0
1
2
3
4
5
6
7
Practice and Problem Solving
with
Homework
Find the sum using a number line.
10. 1 6
Example Exercises
1
10–13
2
14–33
11. 8 (9)
12. 3 (3)
13. 5 (5)
Find the absolute value of the number.
14. 28
Online Resources
15. 100
16. 49
17. 35
18. 2 (5)
19. 0 (4)
20. 3 (7)
21. 10 3
22. 1 (9)
23. 4 (6)
24. 14 8
25. 7 (1)
26. 13 (13)
27. 10 10
28. 1 17
29. 5 (15)
30. 15 (8)
31. 19 (1)
32. 21 (2)
33. 18 (27)
CLASSZONE.COM
• More Examples
• eTutorial Plus
Find the sum.
34. Stocks The table shows the changes in value of a $58 stock in one
week. Write an addition expression that describes the situation.
Then find the value of the stock at the end of the week.
Change in Stock Value
Day of the Week
Change in Value
Monday
up $8
Tuesday
down $12
Wednesday
down $20
Thursday
up $3
Friday
up $4
Copy and complete the statement using <, >, or .
540
Chapter 11
Integers
35. 3 (5) _?_ 4 (2)
36. 8 (1) _?_ 6 3
37. 12 (7) 6 _?_ 5 5 10
38. 9 (4) (3) _?_ 8 (9) (15)
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39. Game Shows In a contest, students gain or lose points by answering
History
questions. You begin with 25 points, you lose 40 points, and then gain
10 points. Write an addition expression that represents the problem.
Then find your score.
Algebra Evaluate the expression when a 6 and b 9.
40. a b
41. b a
42. 11 a b
43. b (8) a
Tell whether the statement is always, sometimes, or never true.
44. The sum of two negative integers is positive.
45. The sum of two positive integers is positive.
46. The sum of a positive integer and a negative integer is zero.
47. Critical Thinking What is the sum of a number and its opposite?
Give examples to support your answer.
■
Game Shows
By 1940 there were 50 quiz
shows on the air. By the end
of the decade there were
200 shows on the air.
Shows like “Dr. IQ” and
“Professor Peter Puzzleworth”
were popular. What was the
increase in the number of
game shows on the air from
1940 to the end of the
decade?
48. Challenge The sum of 7 and another integer is 5. What is the
other integer?
Mixed Review
Find the percent of the number. (Lesson 8.7)
49. 2% of 50
50. 65% of 80
51. 24.5% of 200
52. Draw an obtuse angle. Use a protractor to find the measure of
your angle. (Lessons 9.2, 9.3)
Copy and complete the statement using < or >. (Lesson 11.1)
53. 5 _?_ 5
54. 4 _?_ 1
55. 13 _?_ 19
56. 24 _?_ 0
59. 123 48
60. 301 99
Basic Skills Find the difference.
57. 38 19
58. 52 26
Test-Taking Practice
INTERNET
State Test Practice
CLASSZONE.COM
61. Multiple Choice Which expression does not have a sum of 7?
A. 4 (3)
B. 10 (17)
C. 13 6
D. 5 2
62. Short Response A football team lost 3 yards on the first play, lost
5 yards on the second play, and gained 12 yards on the third play. Did
the team gain the 10 yards needed for a first down? Explain how you
found your answer.
Lesson 11.2
Adding Integers
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