multiplying decimals & properties of multiplication christine berg edited by v t hamilton

Multiplying Multiplying Decimals &Decimals &Properties of Properties of MultiplicationMultiplication

Christine BergChristine BergEdited By V T HamiltonEdited By V T Hamilton

Step 1Step 1::Multiply as if the Multiply as if the

factors were whole factors were whole numbers numbers

Step 1Step 1:: 8.58.5

X2.5X2.5

4 2 54 2 5

1 7 0 01 7 0 0

2 1 2 5 next…..2 1 2 5 next…..

Step 2Step 2::

Count the total Count the total decimals places in decimals places in

the factorsthe factors

Step 1Step 1:: 8.8.55

X2.X2.5 5

4 2 54 2 5

1 7 0 01 7 0 0

2 1 2 5 next…..2 1 2 5 next…..

Step 3Step 3::

Give the product Give the product the total decimal the total decimal

places of the places of the factorsfactors

Step 1Step 1:: 8.8.55

X2.X2.5 5

4 2 54 2 5

1 7 0 01 7 0 0

2 1 2 1 .2 5.2 5

Try These:Try These:

1. 4.8 2. 3.55 x 0.5 x .05

Answers:Answers:

1. 4.8 2. 3.55 x 0.5 x .05

= 2.40 = 0.1775

Properties of Properties of MultiplicationMultiplication

Identity PropertyIdentity Property

The product of 1 and The product of 1 and a number (a number (aa) is the ) is the

number (number (aa))

1(a) = a1(a) = a

ExamplesExamples

1 (b) = b1 (b) = b

1 x 42 = 421 x 42 = 42

Zero PropertyZero Property

The product of 0 and The product of 0 and a number (a number (aa) is 0) is 0

0 (a) = 00 (a) = 0

ExamplesExamples

0 (b) = 00 (b) = 0

0 x 67 = 00 x 67 = 0

Commutative Commutative PropertyProperty

Changing the order Changing the order of the factors does of the factors does

not change the not change the answeranswer

ExamplesExamples

a ( b ) = b ( a )a ( b ) = b ( a )

5 x 2 = 2 x 55 x 2 = 2 x 5

Associative Associative PropertyProperty

Changing the Changing the grouping of factors grouping of factors does not change does not change

the answerthe answer

ExamplesExamples(( a a bb ) ) cc = = aa ( ( bb cc ) )

( 3 x 2 ) x 4 = 3 x ( 2 x 4 )( 3 x 2 ) x 4 = 3 x ( 2 x 4 )

Try These:Try These:Identify the propertyIdentify the property

(( x y x y ) z = ) z = xx ( ( yy zz ) )

0 x 4 = 00 x 4 = 0

Answers:Answers:(( x y x y ) z = ) z = xx ( ( yy zz ) )

Associative Property of xAssociative Property of x

0 x 4 = 00 x 4 = 0

Zero PropertyZero Property