Multiplying Decimals

Lesson 1-7

Problem of the Day: Solve the equations below

:• Find the sum or difference:• 8 - .8 = 12.3 + .123 =

• 3.8 - .99= 3.12- .312=

• 12.56 + 234.56= 8.3+ .99=

Problem of the Day: Solve the equations below

:• In a basketball game Lebron James makes 5

three pointers and 14 two point shots. How many points in total did he score? If his normal average point total per game is 27.6, did he play above or below his average?

LO: Eagle Scholars will be able to multiply decimals

• You do not line up the factors by the decimal point.

• 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

5.633.7x

1

2

4

4

39098

1

16+13

1

8

1

0

1

2

two

one

three.

Example: 0.53 x 2.6182.618 has more digits (4) than 0.53 (3), so it goes on top.

2.6180.53x

4

2

58

1

700

4

90

3

13000000+457

1

831

Decimal Places

three

two

five.

Try This: 6.5 x 15.3

15.36.5x

5

1

6

2

708

1

1

3

9+

54

1

99

one

one

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