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Lesson Reflection
3-6
Math Learning Goal
Students will
understand
decimals.
Students will understand decimals by being
able to do the following:
• Learn to write, compare, and order decimals using place value and
number lines (3-1)
• Learn to estimate decimal sums, differences, products, and
quotients (3-2)
• Learn to add and subtract decimals (3-3)
• Learn to multiply and divide decimals by powers of ten and to
convert metric measurements (3-4)
• Learn to write large numbers in scientific notation (3-5)
• Learn to multiply decimals by
whole numbers and by decimals
(3-6)
3-6 Multiplying Decimals
Today’s Learning Goal Assignment
Learn to multiply
decimals by whole
numbers and by
decimals.
Course 1
3-6 Multiplying Decimals
th
6
Grade Math HW
Page 122
#10-25
Course 1
3-6 Multiplying Decimals
Warm Up
Problem of the Day
Lesson Presentation
Course 1
3-6 Multiplying Decimals
Warm Up
Multiply.
1. 87  320
27,840
2. 943  800
754,400
3. 3,806  10
4. 1,207  100
38,060
120,700
5. 72  196
14,112
6. 120  523
62,760
Course 1
3-6 Multiplying Decimals
Problem of the Day
Carmen and Rita sold homemade
oatmeal cookies. After 8 days, they had
sales totaling $70. Each day, their sales
were $0.50 higher than the previous
day. What were their sales on the first
day?
$7.00
Course 1
3-6 Multiplying Decimals
Today’s Learning Goal Assignment
Learn to multiply
decimals by whole
numbers and by
decimals.
Course 1
3-6 Multiplying Decimals
Additional Example 1: Science Application
Something that weighs 1 lb on Earth weighs
0.17 lb on the Moon. How much would a 4 lb
dumbbell weigh on the Moon?
4  0.17
0.17
0.17
0.17
0.17
+ _____
0.68
Course 1
You can think of multiplication by a
whole number as a repeated
addition.
3-6 Multiplying Decimals
Additional Example 1 Continued
Something that weighs 1 lb on Earth weighs
0.17 lb on the Moon. How much would a 4 lb
dumbbell weigh on the Moon?
You can also multiply as you would with whole
numbers. Place the decimal point by adding the
number of decimal places in the numbers
multiplied.
0.17
4
 _____
0.68
2 decimal places
+ 0 decimal places
2 decimal places
A 4 lb dumbbell on Earth weighs 0.68 lb on the Moon.
Course 1
3-6 Multiplying Decimals
Try This: Example 1
Something that weighs 1 lb on Earth weighs
0.17 lb on the Moon. How much would a 7 lb
dumbbell weigh on the Moon?
7  0.17
0.17
0.17
0.17
0.17
0.17
0.17
0.17
+ _____
1.19
Course 1
You can think of multiplication by a
whole number as a repeated
addition.
3-6 Multiplying Decimals
Try This: Example 1 Continued
Something that weighs 1 lb on Earth weighs
0.17 lb on the Moon. How much would a 7 lb
dumbbell weigh on the Moon?
You can also multiply as you would with whole
numbers. Place the decimal point by adding the
number of decimal places in the numbers
multiplied.
0.17
7
 _____
1.19
2 decimal places
+ 0 decimal places
2 decimal places
A 7 lb dumbbell on Earth weighs 1.19 lb on the Moon.
Course 1
3-6 Multiplying Decimals
Additional Example 2A: Multiplying a Decimal by
a Decimal
Find the product.
A. 0.3  0.4
Multiply. Then place the decimal point.
0.3
1 decimal place
 0.4
+ 1 decimal place
0.12
Course 1
2 decimal places
3-6 Multiplying Decimals
Additional Example 2B: Multiplying a Decimal by
a Decimal
B. 0.07  0.8
0.07  1 = 0.07 Estimate the product. 0.8 is
close to 1.
0.07

0.8
0.056
Multiply. Then place the
decimal point.
2 decimal places
+ 1 decimal place
3 decimal places; use a
placeholder zero
0.056 is close to the estimate of 0.07. The
answer is reasonable.
Course 1
3-6 Multiplying Decimals
Additional Example 2C: Multiplying a Decimal by
a Decimal
C. 1.34  2.5
13=3
1.34
 2.5
670
2680
3.350
Estimate the product. Round
each factor to the nearest
whole number.
Multiply. Then place the
decimal point.
2 decimal places
+ 1 decimal place
3 decimal places
3.350 is close to the estimate of 3. The answer
is reasonable.
Course 1
3-6 Multiplying Decimals
Try This: Example 2A
Find each product.
A. 0.5  0.2
Multiply. Then place the decimal point.
0.5
1 decimal place
 0.2
+ 1 decimal place
0.10
Course 1
2 decimal places
3-6 Multiplying Decimals
Try This: Example 2B
B. 0.03  0.9
0.03  1 = 0.03 Estimate the product. 0.9 is
close to 1.
0.03

0.9
0.027
Multiply. Then place the
decimal point.
2 decimal places
+ 1 decimal place
3 decimal places; use a
placeholder zero
0.027 is close to the estimate of 0.03. The
answer is reasonable.
Course 1
3-6 Multiplying Decimals
Try This: Example 2C
C. 3.80  3.3
4  3 = 12
3.80
 3.3
1140
11400
12.540
Estimate the product. Round
each factor to the nearest
whole number.
Multiply. Then place the
decimal point.
2 decimal places
+ 1 decimal places
3 decimal places
12.54 is close to the estimate of 12. The answer
is reasonable.
Course 1
3-6 Multiplying Decimals
Additional Example 3A: Evaluating Decimal
Expressions
Evaluate 5x for each value of x.
A. x = 3.062
5x = 5(3.062)
Substitute 3.062 for x.
3.062
3 decimal places
5
+ 0 decimal places
15.310
3 decimal places

Remember!
These notations all mean multiply 3 times x.
3•x
Course 1
3x
3(x)
3-6 Multiplying Decimals
Additional Example 3B: Evaluating Decimal
Expressions
B. x = 4.79
5x = 5(4.79)

Course 1
Substitute 4.79 for x.
4.79
2 decimal places
5
+ 0 decimal places
23.95
2 decimal places
3-6 Multiplying Decimals
Try This: Example 3A
Evaluate 5x for each value of x.
A. x = 2.012
5x = 5(2.012)
Substitute 2.012 for x.
2.012
3 decimal places
5
+ 0 decimal places
10.060
3 decimal places

Course 1
3-6 Multiplying Decimals
Try This: Example 3B
B. x = 6.22
5x = 5(6.22)
6.22
2 decimal places
5
+ 0 decimal places
31.10
2 decimal places

Course 1
Substitute 6.22 for x.
3-6 Multiplying
Insert Lesson
Decimals
Title Here
Lesson Quiz
Find each product.
1.
0.8
 0.07
0.056
2. 0.006  0.07
0.00042
Evaluate 8x for each value of x.
3. x = 2.705
21.64
4. x = 0.804
6.432
5. “Pick your own” peaches sell for $0.95
per pound. You picked 92 pounds of
peaches. How much were you charged? $87.40
Course 1