Transcript Chapter 3 Lesson 3

Five-Minute Check (over Lesson 3–2)
Main Idea
Example 1: Real-World Example
Example 2: Real-World Example
Example 3: Compatible Numbers
• I will estimate products by using rounding and
compatible numbers.
Estimate 67 × 32. Round each number to the
nearest ten.
One Way: Round one factor.
THINK It is easier to compute 67 × 30 than 67 × 32.
× 32
67
× 30
67
Round 32 to the nearest ten.
Find 67 ×2,010
30 mentally.
Estimate 67 × 32. Round each number to the
nearest ten.
Another Way: Round both factors.
× 32
67
× 30
Round
70 67 to the nearest ten.
Round 32 to the nearest ten.
Find 70 ×2,100
30 mentally.
Answer: So, depending on how you estimate,
67 × 32 is about 2,010 or 2,100.
Estimate 58 × 42.
A. 2,000
B. 2,400
C. 2,500
D. 3,000
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B
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The students at DeSales Middle School
collected cans for recycling. In one week, each
of the 24 classes collected 189 cans. About
how many cans did they collect that week?
Round each factor to
One Way: its greatest place value.
× 24
189
× 20
Round200
189 to the nearest hundred.
Round 24 to the nearest ten.
Find 200 ×4,000
20 mentally.
Another Way: Round 189 to the nearest hundred.
× 24
189
× 24
Round200
189 to the nearest hundred.
Find 200 ×4,800
24 mentally.
Another Way: Use compatible numbers.
× 24
189
× 25
200 and
20025 are compatible
numbers.
Find 200 ×5,000
25 mentally.
Answer: Depending on how you round, 189 × 24
is about 4,000, 4,800, or 5,000. So, the
students collected between 4,000 and
5,000 cans.
A school collected soup labels for a fund raiser. In
two weeks, each of the 33 classes collected 296
can labels. About how many labels did the school
collect in all?
A. 9,000 labels
B. 9,500 labels
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B
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D. 11,000 labels
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C. 10,000 labels
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Compatible Numbers
Jared earns $24 per week mowing lawns. About
how much does he earn per month?
24 × 4 → 25 × 4
Replace 24 with 25.
24 × 4 = 100
THINK Four quarters are the
same as $1.00. So, 25 × 4 = 100.
Answer: Jared earns about $100 per month.
A car wash is used by 54 cars per day. About how
many cars use the car wash in one month?
A. 900 cars
B. 1,200 cars
C. 1,400 cars
D. 1,500 cars
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B
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End of the Lesson
Five-Minute Check (over Lesson 3–2)
Image Bank
Math Tool Chest
Multiply Mentally
(over Lesson 3–2)
Find 48 × 3 mentally using the Distributive Property.
Show the steps that you used.
A. 3 × (40 + 8) = (3 × 40) + (3 × 8) =
120 + 24 = 144
D. (3 × 40) + (48 × 3) = 264
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C. (3 × 40) + 8 = 120 + 8 = 128
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B. (3 × 40) × (3 × 8) = 120 × 24 =
2,880
(over Lesson 3–2)
Find 5 × 64 mentally using the Distributive Property.
Show the steps that you used.
A. (5 × 60) × (5 × 4) = 300 × 20 =
6,000
B. (5 × 60) + 4 = 300 + 4 = 304
D. (5 × 60) + (64 × 5) = 1,820
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C. 5 × (60 + 4) = (5 × 60) + (5 × 4) =
300 + 20 = 320
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(over Lesson 3–2)
Find 87 × 4 mentally using the Distributive Property.
Show the steps that you used.
A. (4 × 80) × (4 × 7) = 320 × 28 =
8,960
D. (4 × 87) + (4 × 80) = 668
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C. (4 × 80) + 7 = 320 + 7 = 327
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B. 4 × (80 + 7) = (4 × 80) + (4 × 7) =
320 + 28 = 348
(over Lesson 3–2)
Find 6 × 54 mentally using the Distributive Property.
Show the steps that you used.
A. 6 × (50 + 4) = (6 × 50) + (6 × 4) =
300 + 24 = 324
D. (6 × 54) + (6 × 50) = 324 + 300 = 624
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C. (6 × 50) + 4 = 300 + 4 = 304
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B. (6 × 50 × 4) = (6 × 50) × (6 × 4) =
300 × 24 = 7,200