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.

67× 32 × 30

67

2,010Round 32 to the nearest ten.Find 67 × 30 mentally.

Estimate 67 × 32. Round each number to the nearest ten.

Another Way: Round both factors.

67× 32 × 30

70

2,100

Round 67 to the nearest ten.

Find 70 × 30 mentally.Round 32 to the nearest ten.

Answer: So, depending on how you estimate, 67 × 32 is about 2,010 or 2,100.

1. A

2. B

3. C

4. D

A B C D

0% 0%0%0%

Estimate 58 × 42.

A. 2,000

B. 2,400

C. 2,500

D. 3,000

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?

189× 24 × 20

200

4,000

Round 189 to the nearest hundred.

Find 200 × 20 mentally.

One Way:Round each factor to its greatest place value.

Round 24 to the nearest ten.

189× 24 × 24

200

4,800

Round 189 to the nearest hundred.

Find 200 × 24 mentally.

Another Way: Round 189 to the nearest hundred.

189× 24 × 25

200

5,000

200 and 25 are compatible numbers.

Find 200 × 25 mentally.

Another Way: Use compatible numbers.

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.

1. A

2. B

3. C

4. D0% 0%0%0%

A. 9,000 labels

B. 9,500 labels

C. 10,000 labels

D. 11,000 labels

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?

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.

1. A

2. B

3. C

4. D0% 0%0%0%

A. 900 cars

B. 1,200 cars

C. 1,400 cars

D. 1,500 cars

A car wash is used by 54 cars per day. About how many cars use the car wash in one month?

End of the Lesson

Five-Minute Check (over Lesson 3–2)

Image Bank

Math Tool Chest

Multiply Mentally

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3–2)

A. 3 × (40 + 8) = (3 × 40) + (3 × 8) = 120 + 24 = 144

B. (3 × 40) × (3 × 8) = 120 × 24 = 2,880

C. (3 × 40) + 8 = 120 + 8 = 128

D. (3 × 40) + (48 × 3) = 264

Find 48 × 3 mentally using the Distributive Property. Show the steps that you used.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3–2)

A. (5 × 60) × (5 × 4) = 300 × 20 = 6,000

B. (5 × 60) + 4 = 300 + 4 = 304

C. 5 × (60 + 4) = (5 × 60) + (5 × 4) = 300 + 20 = 320

D. (5 × 60) + (64 × 5) = 1,820

Find 5 × 64 mentally using the Distributive Property. Show the steps that you used.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3–2)

A. (4 × 80) × (4 × 7) = 320 × 28 = 8,960

B. 4 × (80 + 7) = (4 × 80) + (4 × 7) = 320 + 28 = 348

C. (4 × 80) + 7 = 320 + 7 = 327

D. (4 × 87) + (4 × 80) = 668

Find 87 × 4 mentally using the Distributive Property. Show the steps that you used.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3–2)

A. 6 × (50 + 4) = (6 × 50) + (6 × 4) = 300 + 24 = 324

B. (6 × 50 × 4) = (6 × 50) × (6 × 4) = 300 × 24 = 7,200

C. (6 × 50) + 4 = 300 + 4 = 304

D. (6 × 54) + (6 × 50) = 324 + 300 = 624

Find 6 × 54 mentally using the Distributive Property. Show the steps that you used.