4.16.24 21st Century Movements for Black Lives.pptx
Math Gr4 Ch8
1. Chapter 8
Multiply by Two-Digit Numbers
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2. Multiply by Two-Digit Numbers
8
Lesson 8-1 Multiply by Tens
Lesson 8-2 Estimate Products
Lesson 8-3 Problem-Solving Strategy: Act It Out
Lesson 8-4 Multiply Two-Digit Numbers
Lesson 8-5 Multiply Three-Digit Numbers by
Two-Digit Numbers
Lesson 8-6 Problem-Solving Investigation:
Choose a Strategy
Lesson 8-7 Multiply Greater Numbers
3. 8-1 Multiply by Tens
Five-Minute Check (over Chapter 7)
Main Idea
California Standards
Example 1
Example 2
4. 8-1 Multiply by Tens
• I will multiply a whole number by a multiple of ten.
5. 8-1 Multiply by Tens
Standard 4NS3.3 Solve problems
involving the multiplication of multidigit
numbers by two-digit numbers.
6. 8-1 Multiply by Tens
Standard 4NS3.2 Demonstrate an
understanding of, and the ability to use,
standard algorithms for multiplying a multidigit
number by a two-digit number and for dividing a
multidigit number by a one-digit number; use
relationships between them to simplify computations
and to check results.
7. 8-1 Multiply by Tens
There are 35 packs of markers in an art classroom.
Each pack contains 50 markers. How many markers
are there in all?
You need to find 35 50.
8. 8-1 Multiply by Tens
One Way: Use Properties
35 × 50 Write the problem.
35 × (10 × 5) Think of 50 as 10 × 5.
35 × (5 × 10) Commutative Property
(35 × 5) × 10 Associative Property
175 × 10 Multiply. 35 × 5 = 175
1,750 Mental Math.
9. 8-1 Multiply by Tens
Another Way: Paper and Pencil
Step 1 Multiply the Step 2 Multiply the
ones. tens.
35 35
× 50 × 50
0 1,75 0
Answer: So, there are 1,750 markers in all.
10. 8-1 Multiply by Tens
Find 45 30.
A. 1,350
B. 1,250
C. 135
D. 125
11. 8-1 Multiply by Tens
A store has 20 children’s bicycles in stock that
cost $159 each. How much do all of the bicycles
cost altogether?
Step 1 Multiply the ones.
$159
20
0
12. 8-1 Multiply by Tens
Step 2 Multiply the tens.
$159
20
$3,18 0
Answer: So, all of the bicycles cost $3,180.
13. 8-1 Multiply by Tens
Check
Think of 20 × 159 as 2 × 10 × 159.
20 × $159 Write the problem.
(2 × 10) × $159 Think of 20 as 2 × 10.
(10 × 2) × $159 Commutative Property
10 × (2 × $159) Associative Property
10 × $318 Multiply. 2 × $159 = $318.
$3,180 Mental Math
So, the answer is correct.
14. 8-1 Multiply by Tens
Find $179 30.
A. $6,370
B. $5,530
C. $5,370
D. $4,170
15.
16. 8-2 Estimate Products
Five-Minute Check (over Lesson 8-1)
Main Idea
California Standards
Example 1
Example 2
17. 8-2 Estimate Products
• I will estimate products by rounding.
18. 8-2 Estimate Products
Standard 4NS3.3 Solve problems involving
multiplication of multidigit numbers by two-digit
numbers.
Standard 4NS1.3 Round whole numbers
through the millions to the nearest
ten, hundred, thousand, ten thousand, or
hundred thousand.
19. 8-2 Estimate Products
Kaylee is awake for about 16 hours each day.
About how many hours is she awake in 3 weeks?
There are 21 days in 3 weeks. So, estimate 16 21.
Round each factor to its greatest place. Then multiply.
Step 1 Round each factor to the nearest ten.
16 20
21 20
20. 8-2 Estimate Products
Step 2 Multiply.
20
20
400
Answer: So, Kaylee is awake for about 400 hours
in 3 weeks.
21. 8-2 Estimate Products
A koala sleeps for about 19 hours a day. About
how many hours does one sleep in 3 weeks?
A. 400
B. 425
C. 450
D. 500
22. 8-2 Estimate Products
A company bought 53 computers for $909 each.
About how much did they spend in all? You need
to estimate $909 × 53.
Step 1 Round each factor to its greatest place.
909 900
53 50
23. 8-2 Estimate Products
Step 2 Multiply.
900
50
45,000
Answer: So, the company spent about $45,000.
24. 8-2 Estimate Products
A school bought 57 laptops for $837 each. About
how much did the school spend in all?
A. $45,000
B. $48,000
C. $53,000
D. $56,000
25.
26. 8-3 Problem-Solving Strategy: Act It Out
Five-Minute Check (over Lesson 8-2)
Main Idea
California Standards
Example 1: Problem-Solving Strategy
27. 8-3 Problem-Solving Strategy: Act It Out
• I will solve a problem by acting it out.
28. 8-3 Problem-Solving Strategy: Act It Out
Standard 4MR2.3 Use a variety of methods,
such as words, numbers, symbols, charts,
graphs, tables, diagrams, and models, to
explain mathematical reasoning.
29. 8-3 Problem-Solving Strategy: Act It Out
Standard 4NS3.0 Students solve problems
involving addition, subtraction, multiplication, and
division of whole numbers and understand the
relationships among the operations.
30. 8-3 Problem-Solving Strategy: Act It Out
Sonoda has 6 coins in his
bank. The coins equal 65¢.
What combination of coins
does he have in his bank?
31. 8-3 Problem-Solving Strategy: Act It Out
Understand
What facts do you know?
• Sonoda has 6 coins.
• The value of the 6 coins is 65¢.
What do you need to find?
• Find the coins Sonoda has in his bank.
32. 8-3 Problem-Solving Strategy: Act It Out
Plan
You can use play money to act out different
combinations of 65¢.
33. 8-3 Problem-Solving Strategy: Act It Out
Solve
One way to make 65¢ is
with 2 quarters, 1 dime,
and 1 nickel. But, that is
the only 4 coins. You
need two more coins.
34. 8-3 Problem-Solving Strategy: Act It Out
Solve
Take 1 quarter and
exchange it for 2
dimes and 1 nickel.
The value stays the
same, and the number
of coins increases to 6.
Answer: So, Sonoda has 1 quarter, 3 dimes, and
2 nickels.
35. 8-3 Problem-Solving Strategy: Act It Out
Check
Look back at the problem.
1 quarter + 3 dimes + 2 nickels
= (1 × 25 ) + (3 × 10 ) + (2 × 5 )
= 25 + 30 + 10
= 65
So, the answer is correct.
36.
37. 8-4 Multiply Two-Digit Numbers
Five-Minute Check (over Lesson 8-3)
Main Idea
California Standards
Example 1
Example 2
38. 8-4 Multiply Two-Digit Numbers
• I will multiply two-digit numbers.
39. 8-4 Multiply Two-Digit Numbers
Standard 4NS3.2 Demonstrate an
understanding of, and the ability to use, standard
algorithms for multiplying a multidigit number by a
two-digit number and for dividing a multidigit
number by a one-digit number; use the relationships
between them to simplify computations and to
check results.
40. 8-4 Multiply Two-Digit Numbers
Preparation for Standard 4NS3.3 Solve
problems involving multiplication of multidigit
numbers by two-digit numbers.
41. 8-4 Multiply Two-Digit Numbers
How far can a truck travel in 14 hours if it is
traveling an average of 57 miles per hour?
43. 8-4 Multiply Two-Digit Numbers
One Way: Partial Products
44. 8-4 Multiply Two-Digit Numbers
Another Way: Paper and Pencil
Step 1 Multiply the ones.
2
57
× 14
228
45. 8-4 Multiply Two-Digit Numbers
Another Way: Paper and Pencil
Step 2 Multiply the tens.
2
57
× 14
228
570
46. 8-4 Multiply Two-Digit Numbers
Another Way: Paper and Pencil
Step 3 Add the 2
products. 57
× 14
228
+ 570
798
Answer: So, the truck can travel 798 miles in
14 hours at 57 miles per hour.
47. 8-4 Multiply Two-Digit Numbers
How far can a car travel in 15 hours if it is traveling
an average of 63 miles per hour?
A. 368
B. 378
C. 935
D. 945
48. 8-4 Multiply Two-Digit Numbers
The Jones family spends an average of $48 a
month going to the movies. How much does the
family spend in 3 years?
Estimate 50 × 40 = 2,000.
Step 1 Multiply the ones.
$48
36
288
50. 8-4 Multiply Two-Digit Numbers
Step 3 Add the products.
$48
36
288
+ 1,440
1,728
Answer: So, the Jones family spends $1,728 in
3 years.
51. 8-4 Multiply Two-Digit Numbers
Check
1,200 + 240 + 240 + 48 = 1,728
Check for Reasonableness
Since 1,728 is close to the estimate of 2,000, the
answer is reasonable.
52. 8-4 Multiply Two-Digit Numbers
Lauren spends about $72 a month on gas for her
car. How much does she spend on gas in 4 years?
A. $3,456
B. $3,157
C. $2,456
D. $2,157
53.
54. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Five-Minute Check (over Lesson 8-4)
Main Idea
California Standards
Example 1
Example 2
55. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
• I will multiply a three-digit number by a two-digit
number.
56. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Standard 4NS3.2 Demonstrate an
understanding of, and the ability to use,
standard algorithms for multiplying a multidigit
number by a two-digit number and for dividing a
multidigit number by a one-digit number; use the
relationships between them to simplify computations
and to check results.
57. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Standard 4NS3.3 Solve problems involving
multiplication of multidigit numbers by two-digit
numbers.
58. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Antonio spends 194 minutes taking piano lesson
each month. How many minutes does he spend
taking piano lesson in a year?
Estimate 12 × 194 10 × 200 = 2,000.
Step 1 Multiply 194 by 2.
194
12
388
60. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Answer: So, Antonio spends 2,328 minutes taking
piano lessons in a year.
61. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Check for Reasonableness
Since 2,328 is close to the estimate, 2,000. So,
the answer is correct.
62. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Lui spends about 321 minutes a month writing
to pen pals. How many minutes does he spend
writing letters in a year?
A. 3,210
B. 3,814
C. 3,752
D. 3,852
63. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Rai is paid $308 a week for her part-time job at the
city library. What is Rai’s annual salary?
Estimate $308 × 52 300 × 50 = $15,000.
Step 1 Multiply $308 by 2.
1
$308
52
$616
64. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Step 2 Multiply $308 by 50.
4
1
$308
52
$616
$15,400
65. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Step 3 Add the partial products.
4
1
$308
52
$616
+ $15,400
$16,016
Answer: So, the product of $308 and 52 is $16,016.
66. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Check for Reasonableness
Since $16,016 is close to the estimate, the answer
is reasonable.
67. 8-5 Multiply Three-Digit Numbers by Two-Digit Numbers
Monique gets paid $444 a week at her job. How
much does she get paid in a year?
A. $22,088
B. $23,088
C. $21,088
D. $20,088
68.
69. 8-6 Problem-Solving Investigation: Choose a Strategy
Five-Minute Check (over Lesson 8-5)
Main Idea
California Standards
Example 1: Problem-Solving Investigation
70. 8-6 Problem-Solving Investigation: Choose a Strategy
• I will choose the best strategy to solve a problem.
71. 8-6 Problem-Solving Investigation: Choose a Strategy
Standard 4MR1.1 Analyze problems by
identifying relationships, distinguishing relevant
from irrelevant information, sequencing and
prioritizing information, and observing patterns.
72. 8-6 Problem-Solving Investigation: Choose a Strategy
Standard 4NS3.0 Students solve problems
involving addition, subtraction, multiplication, and
division of whole numbers and understand the
relationships among the operations.
73. 8-6 Problem-Solving Investigation: Choose a Strategy
GREGORY: I spent 4 hours at a
school carnival. I spent 35 minutes
eating and 45 minutes playing
games. I also rode 12 rides, which
took about 15 minutes each because
I had to stand in lines.
YOUR MISSION: Determine if Gregory
is correct in saying that he spent
4 hours at the carnival.
74. 8-6 Problem-Solving Investigation: Choose a Strategy
Understand
What facts do you know?
• Gregory spent 35 minutes eating.
• He spent 45 minutes playing games.
• He rode 12 rides, which lasted 15 minutes each.
What do you need to find?
• Find if Gregory is correct in saying he spent
4 hours at the carnival.
75. 8-6 Problem-Solving Investigation: Choose a Strategy
Plan
Find the total number of minutes spent on
carnival activities and compare to 4 hours.
76. 8-6 Problem-Solving Investigation: Choose a Strategy
Solve
Gregory gave the amount of time spent at the
carnival in hours. The amount of time spent on
each activity was given in minutes. So, change
hours to minutes. Then compare the two
amounts of time.
77. 8-6 Problem-Solving Investigation: Choose a Strategy
Solve
60 minutes 15
60 minutes × 12 35 minutes
60 minutes 30 45 minutes
+ 60 minutes + 150 + 180 minutes
240 minutes 180 230 minutes
time Gregory said time spent time spent on
he spent at carnival riding rides carnival activities
78. 8-6 Problem-Solving Investigation: Choose a Strategy
Solve
The amount of time Gregory said he spent at
the carnival does not equal the amount of time
he spent of carnival activities.
Answer: So, Gregory was not correct.
79. 8-6 Problem-Solving Investigation: Choose a Strategy
Check
Look back at the problem. Use subtraction to
check the amount of time spent on carnival
activities.
133 – 55 – 46 – 32 = 0. So, Gregory was not
correct.
80.
81. 8-7 Multiply Greater Numbers
Five-Minute Check (over Lesson 8-6)
Main Idea
California Standards
Example 1
Example 2
82. 8-7 Multiply Greater Numbers
• I will multiply four- and five-digit numbers by a
two-digit number.
83. 8-7 Multiply Greater Numbers
Standard 4NS3.3 Solve problems involving
multiplication of multidigit numbers by two-digit
numbers.
Standard 4MR2.1 Use estimation to verify the
reasonableness of calculated results.
84. 8-7 Multiply Greater Numbers
A science museum gets an average of 4,562
visitors every week. How many visitors does
it get in a year?
Estimate 52 4,562 50 × 5,000 = 250,000
Step 1 Multiply the ones. Regroup if necessary.
1 11
4,562
52
9,124
86. 8-7 Multiply Greater Numbers
Step 3 Add the partial products. Check for
reasonableness.
2 3
1 11
4,562
52
9,124
+ 228,100
237,224
Answer: So, the science museum gets 237,224
visitors a year.
87. 8-7 Multiply Greater Numbers
Check for Reasonableness
Since the answer, 237,224, is close to the estimate,
the answer is reasonable.
88. 8-7 Multiply Greater Numbers
An amusement park gets an average of 8,225
visitors every week. How many visitors does
it get in a year?
A. 427,700
B. 427,590
C. 426,790
D. 427,800
89. 8-7 Multiply Greater Numbers
A web site gets an average of 23,146 hits each
month. How many hits does it get in 15 months?
Estimate 15 23,149 20 × 20,000 = 400,000
Step 1 Multiply the ones. Regroup if necessary.
1 24
23,149
15
115,745
91. 8-7 Multiply Greater Numbers
Step 3 Add the partial products.
1 24
23,149
15
115,745
+ 231,490
347,235
Answer: So, the website gets 347,235 hits in
15 months.
92. 8-7 Multiply Greater Numbers
Check for Reasonableness
Since 347,235 is close to the estimate, the answer
is reasonable.
93. 8-7 Multiply Greater Numbers
Another web site gets an average of 19,225 hits a
day. How many hits does the website get in a 31
day month?
A. 594,975
B. 595,864
C. 595,975
D. 594,323
97. Multiply by Two-Digit Numbers
8
(over Chapter 7)
Multiply. Check for reasonableness.
203
2
A. 426
B. 405
C. 406
D. 425
98. Multiply by Two-Digit Numbers
8
(over Chapter 7)
Multiply. Check for reasonableness.
506
7
A. 1,283
B. 3,502
C. 1,273
D. 3,542
99. Multiply by Two-Digit Numbers
8
(over Chapter 7)
Multiply. Check for reasonableness.
3 7,035
A. 21,105
B. 21,095
C. 10,368
D. 21,405
100. Multiply by Two-Digit Numbers
8
(over Chapter 7)
Multiply. Check for reasonableness.
8 $4,209
A. $32,743
B. $33,672
C. $13,097
D. $33,752
101. Multiply by Two-Digit Numbers
8
(over Chapter 7)
Multiply. Check for reasonableness.
6 5,008
A. 30,042
B. 30,108
C. 30,708
D. 30,048
102. Multiply by Two-Digit Numbers
8
(over Lesson 8-1)
Multiply.
87
10
A. 807
B. 187
C. 870
D. 957
103. Multiply by Two-Digit Numbers
8
(over Lesson 8-1)
Multiply.
34
30
A. 1,020
B. 912
C. 102
D. 1,054
104. Multiply by Two-Digit Numbers
8
(over Lesson 8-1)
Multiply.
65
80
A. 5,240
B. 520
C. 5,265
D. 5,200
105. Multiply by Two-Digit Numbers
8
(over Lesson 8-1)
Multiply.
$23
50
A. $1,173
B. $115
C. $1,150
D. $1,138
106. Multiply by Two-Digit Numbers
8
(over Lesson 8-1)
Multiply.
$79
90
A. $6,480
B. $7,110
C. $711
D. $7,189
107. Multiply by Two-Digit Numbers
8
(over Lesson 8-1)
Multiply.
$57
60
A. $3,420
B. $3,042
C. $3,477
D. $3,480
108. Multiply by Two-Digit Numbers
8
(over Lesson 8-2)
Estimate. Tell whether the estimate is more or less
than the actual product.
39
35
A. 1,400; more
B. 1,600; less
C. 1,600; more
D. 1,200; less
109. Multiply by Two-Digit Numbers
8
(over Lesson 8-2)
Estimate. Tell whether the estimate is more or less
than the actual product.
63
44
A. 2,700; less
B. 2,400; less
C. 3,000; more
D. 2,700; more
110. Multiply by Two-Digit Numbers
8
(over Lesson 8-2)
Estimate. Tell whether the estimate is more or less
than the actual product.
$54
81
A. $4,300; less
B. $4,400; less
C. $4,800; more
D. $4,000; less
111. Multiply by Two-Digit Numbers
8
(over Lesson 8-2)
Estimate. Tell whether the estimate is more or less
than the actual product.
$274 16
A. $5,400; more
B. $3,000; less
C. $6,000; more
D. $4,125; less
112. Multiply by Two-Digit Numbers
8
(over Lesson 8-2)
Estimate. Tell whether the estimate is more or less
than the actual product.
719 94
A. 63,000; less
B. 64,800; more
C. 70,000; more
D. 64,800; less
113. Multiply by Two-Digit Numbers
8
(over Lesson 8-3)
Solve. Use the Act it Out strategy. Carlos has 8
coins in his pocket. The total value of the coins is
73¢. What coins does Carlos have?
A. 1 quarter, 4 dimes, 1 nickel, 3 pennies
B. 2 quarters, 1 dime, 2 nickels, 3 pennies
C. 3 dimes, 2 nickels, 3 pennies
D. 2 quarters, 2 dimes, 3 pennies
114. Multiply by Two-Digit Numbers
8
(over Lesson 8-4)
Multiply.
17
11
A. 308
B. 34
C. 187
D. 200
115. Multiply by Two-Digit Numbers
8
(over Lesson 8-4)
Multiply.
35
24
A. 840
B. 210
C. 720
D. 740
116. Multiply by Two-Digit Numbers
8
(over Lesson 8-4)
Multiply.
59
46
A. 2,708
B. 590
C. 2,995
D. 2,714
117. Multiply by Two-Digit Numbers
8
(over Lesson 8-4)
Multiply.
$64
37
A. $2,248
B. $2,368
C. $640
D. $2,512
118. Multiply by Two-Digit Numbers
8
(over Lesson 8-4)
Multiply.
$77
66
A. $5,082
B. $4,242
C. $942
D. $4,642
119. Multiply by Two-Digit Numbers
8
(over Lesson 8-4)
Multiply.
92
84
A. 1,936
B. 7,628
C. 1,104
D. 7,728
120. Multiply by Two-Digit Numbers
8
(over Lesson 8-5)
Multiply.
124
13
A. 4,852
B. 1,612
C. 496
D. 1,602
121. Multiply by Two-Digit Numbers
8
(over Lesson 8-5)
Multiply.
206
32
A. 6,482
B. 1,030
C. 5,810
D. 6,592
122. Multiply by Two-Digit Numbers
8
(over Lesson 8-5)
Multiply.
557
45
A. 25,065
B. 24,865
C. 5,013
D. 22,635
123. Multiply by Two-Digit Numbers
8
(over Lesson 8-5)
Multiply.
648
74
A. 47,948
B. 7,128
C. 47,952
D. 45,322
124. Multiply by Two-Digit Numbers
8
(over Lesson 8-5)
Multiply.
817
77
A. 17,534
B. 62,469
C. 11,438
D. 62,909
125. Multiply by Two-Digit Numbers
8
(over Lesson 8-5)
Multiply.
993
86
A. 13,902
B. 85,398
C. 74,398
D. 77,688
126. Multiply by Two-Digit Numbers
8
(over Lesson 8-6)
Use any strategy to solve. Nitin spent 55 minutes
mowing the lawn, 48 minutes cleaning his room, 23
minutes vacuuming, and 32 minutes doing laundry.
Is it reasonable to say that Nitin spent 3 hours on
completing his chores?
A. Yes, it is reasonable because he spent exactly 3
hours completing his chores.
B. No, it is not reasonable because he spent over
3 hours completing his chores.
127. Multiply by Two-Digit Numbers
8
(over Lesson 8-6)
Use any strategy to solve. Nitin spent 55 minutes
mowing the lawn, 48 minutes cleaning his room, 23
minutes vacuuming, and 32 minutes doing laundry.
Is it reasonable to say that Nitin spent 3 hours on
completing his chores?
C. No, it is not reasonable because he spent less
than 3 hours completing his chores.
D. Yes, it is reasonable because he spent almost
3 hours completing his chores.
128. Multiply by Two-Digit Numbers
8
(over Lesson 8-6)
Use any strategy to solve. Nitin spent 55 minutes
mowing the lawn, 48 minutes cleaning his room, 23
minutes vacuuming, and 32 minutes doing laundry.
Is it reasonable to say that Nitin spent 3 hours on
completing his chores?
C. No, it is not reasonable because he spent less
than 3 hours completing his chores.