Name Class 2-1
Date Multiplying Decimals
Modeling
Essential question: How do you multiply decimals?
MCC6.NS.3
1
EXPLORE
Modeling Decimal Multiplication
video tutor
Use decimal grids or area models to find each product.
A
0.3
Shade 3 columns of the grid to represent 0.3.
Shade
The shadings overlap
This represents
0.3 × 0.5 =
B
© Houghton Mifflin Harcourt Publishing Company
0.3 × 0.5
rows of the grid to represent 0.5.
square(s).
hundredth(s), or 0.15.
3.2 × 2.1
3.2
Each row contains 3 wholes + 2 tenths.
Each column contains
The entire area model represents
0.5
whole(s) +
whole(s) +
tenth(s) +
tenth(s).
2.1
hundredth(s).
3.2 × 2.1 =
TRY THIS!
1a. Use the grid to multiply 0.3 × 0.8.
1b. Draw an area model to multiply 2.2 × 4.3.
0.3 × 0.8 =
2.2 × 4.3 =
Module 2
21
Lesson 1
REFLECT
1c. How are the products 2.1 × 3.2 and 21 × 32 alike? How are they different?
To multiply decimals, first multiply as you would with whole numbers. Then
place the decimal point in the product. The number of decimal places in the
product equals the sum of the number of decimal places in the factors.
MCC6.NS.3
2
EXAMPLE
Multiplying Decimals
Dwight bought 2.4 pounds of grapes. The grapes cost $1.95 per pound.
What was the total cost of Dwight’s grapes?
← 2 decimal places
decimal place(s)
←+
1.95
× 2.4
780
+ 3900
4.680
← The grapes cost $
decimal place(s)
.
TRY THIS!
Multiply.
2a.
2b.
× 15.3
378
←
decimal place(s)
9.76
←
decimal place(s)
←+
decimal place(s)
× 0.46
←+
decimal place(s)
← decimal place(s)
+
+
←
decimal place(s)
REFLECT
2c. How can you use estimation to check that you have placed the decimal point
correctly in your product?
Module 2
22
Lesson 1
© Houghton Mifflin Harcourt Publishing Company
12.6
MCC6.NS.3
3
EXAMPLE
Multiplying Decimals
A tree grows 9.25 inches per year. If the tree continues to grow at this
rate, how much will the tree grow in 3.75 years?
9.25 ←
× 3.75 ← +
4625
64750
decimal place(s)
decimal place(s)
+
← decimal place(s)
The tree will grow
inches in 3.75 years.
Estimate to check whether your answer is reasonable:
Round 9.25 to the nearest whole number.
Round 3.75 to the nearest whole number.
Multiply the whole numbers.
Is the answer reasonable? Explain.
TRY THIS!
Multiply.
© Houghton Mifflin Harcourt Publishing Company
3a. 7.14
× 6.78
5712
+
3b. 11.49
× 8.27
+
3c. Rico bicycles at an average speed of 15.5 miles per hour.
miles
What distance will Rico bicycle in 2.5 hours?
3d. Use estimation to show that your answer to 3c is reasonable.
REFLECT
3e. Compare the products 6.95 × 38.3 and 69.5 × 3.83. What do you
notice? Explain.
Module 2
23
Lesson 1
pra c t i c e
1. Use the grid to multiply 0.4 × 0.7.
2. Draw an area model to multiply 1.1 × 2.4.
0.4 × 0.7 =
1.1 × 2.4 =
Place the decimal point in each product.
3. 3.9 × 4.6 = 1 7 9 4
4. 0.219 × 6.2 = 1 3 5 7 8
5. 14.9 × 0.092 = 1 3 7 0 8
6. 5.546 × 8.14 = 4 5 1 4 4 4 4
Multiply.
8. 35.15 × 3.7 =
9. 0.96 × 0.12 =
10. 62.19 × 32.5 =
11. 3.4 × 4.37 =
12. 3.762 × 0.66 =
13. 11.89 × 41 =
14. 73.8 × 19.85 =
15. 12.7 × 1.83 =
16. 44.1 × 24.66 =
17. Chan Hee bought 3.4 pounds of coffee that cost $6.95
per pound. How much did he spend on coffee?
$
18. Adita earns $9.40 per hour working at an animal shelter.
How much money will she earn for 18.5 hours of work?
$
Catherine tracked her gas purchases for one month.
19. How much did Catherine spend on gas
in week 2?
$
Gallons
Cost per
gallon ($)
Week 1
10.4
2.65
20. How much more did she spend in week 4
than in week 1?
Week 2
11.5
2.54
Week 3
9.72
2.75
Week 4
10.6
2.70
$
Module 2
24
Lesson 1
© Houghton Mifflin Harcourt Publishing Company
7. 0.18 × 0.06 =
Name Class 2-1
Date Name ________________________________________ Date __________________ Class__________________
Decimals Practice
Additional
LESSON
4
Practice B: Multiplying Decimals
Find each product.
1.
0.7
 0.3
2.
________________________
4.
3.5
 0.2
5.
12.1
 0.01
8. 2.15 • 1.5
9.0
 0.9
________________________
9. 1.73 • 0.8
_______________________
11. 3.96 • 0.4
________________________
8.0
 0.02
________________________
6.
_______________________
________________________
10. 6.017 • 2.0
3.
_______________________
________________________
7. 0.04 • 0.58
0.05
 0.4
________________________
12. 0.7 • 0.009
_______________________
________________________
Evaluate 8x for each value of x.
13. x  0.5
________________________
16. x  3.12
© Houghton Mifflin Harcourt Publishing Company
© Houghton Mifflin Harcourt Publishing Company
________________________
14. x  2.3
15. x  0.74
_______________________
17. x  0.587
18. x  14.08
_______________________
19. The average mail carrier walks
4.8 kilometers in a workday. How far
do most mail carriers walk in a 6-day
week? There are 27 working days in
July, so how far will a mail carrier
walk in July?
________________________
________________________
20. A deli charges $3.45 for a pound
of turkey. If Tim wants to purchase
2.4 pounds, how much will it cost?
________________________________________
________________________________________
________________________________________
________________________________________
Module 2
25
17
Practice and Problem Solving
Holt McDougal Mathematics
Name ________________________________________ Date __________________ Class __________________
Decimals
Problem
Solving
LESSON
4
Problem Solving: Multiplying Decimals
Use the table to answer the questions.
United States Minimum Wage
1. At the minimum wage, how much did
a person earn for a 40-hour
workweek in 1950?
________________________________________
2. At the minimum wage, how much did
a person earn for working 25 hours in
1970?
________________________________________
Year
1940
1950
1960
1970
1980
1990
2000
Hourly Rate
$0.30
$0.75
$1.00
$1.60
$3.10
$3.80
$5.15
4. About how many times higher was
the minimum wage in 1960 than in
1940?
3. If you had a minimum-wage job in
1990, and worked 15 hours a week,
how much would you have earned
each week?
________________________________________
________________________________________
Circle the letter for the correct answer.
6. Marci’s mother had a minimum-wage
job in 1980. She worked 12 hours a
week. How much did Marci’s mother
earn each week?
A $12.00
F $3.72
B $624.00
G $37.00
C $642.00
H $37.10
D $6,240.00
J $37.20
7. Having one dollar in 1960 is
equivalent to having $5.82 today. If
you worked 40 hours a week in 1960
at minimum wage, how much would
your weekly earnings be worth today?
8. In 2000, Cindy had a part-time job at
a florist, where she earned minimum
wage. She worked 18 hours each
week for the whole year. How much
did she earn from this job in 2000?
A $40.00
F $927.00
B $5.82
G $4,820.40
C $232.80
H $10,712.00
D $2,328.00
J $2,142.40
Module 2
2617
Practice
Problem
Solving
Holtand
McDougal
Mathematics
© Houghton Mifflin Harcourt Publishing Company
© Houghton Mifflin Harcourt Publishing Company
5. Ted’s grandfather had a minimumwage job in 1940. He worked 40 hours
a week for the entire year. How much
did Ted’s grandfather earn in 1940?