Transcript Multiplying Decimals - Fairfield

Multiplying Decimals
Lesson 1-7
To Multiply:
• You do not line up the factors by the decimal.
• Instead, place the number with more digits on
top.
• Line up the other number underneath, at the
right.
• Multiply
• Count the number of decimal places (from the
right) in each factor.
• Use the total number of decimal places in
your two factors to place the decimal in your
product.
Example: 5.63 x 3.7
1
4 2
5.63
x 37
39 4 1
+ 168 9 0
20.8 31
.
two
one
1 1
1
three
Example: 0.53 x 2.618
2.618 has more digits (4) than 0.53 (3), so it goes on top.
3
1
4
2
2 618
x 0 53
7 854
130 900
+ 000 000
1.38 754
.
.
Decimal Places
three
two
1
five
Try This: 6.5 x 15.3
3 1
2 1
15.3
x 6.5
76 5
+ 918 0
9 9.4 5
one
one
1
two
Multiplication Properties
Commutative Property of Multiplication: Factors can be multiplied
in any order.
Example: 12 x 5 = 5 x 12
Associative Property of Multiplication: Factors can be grouped in
any way.
Example: (2 x 3) x 5 = 2 x (3 x 5)
Identity Property of Multiplication: The product of any number and
one is that number.
Example: 18 x 1 = 18
Homework Time
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