# Multiplying and Dividing Decimals

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Multiplying and Dividing Decimals
Section 1-3 (Pages 17-22)

Review… Estimate each quotient using compatible numbers. 1. 24.8 ÷ 4.9

Properties of Multiplication
Identity Property The product of 1 and “a” is “a”. 5 x 1 = 5 1 x 5 = 5 Zero Property The product of 0 and any number is 0. 5 x 0 = 0 0 x 5 = 0

Properties of Multiplication
Commutative Property Changing the order of factors does not change the product. 5 x 2 = 2 x 5 Associative Property Changing the grouping of factors does not change the product. (3 x 2) x 5 = 3 x (2 x 5)

To multiply decimals… Step 1: Multiply as if the factors are whole numbers. Step 2: Add the number of the decimal places in both factors to find the number of decimal places in the product.

Example Find the product of 0.2 x 0.7
Step 1: Multiply as with whole numbers. 2 x 7 14 Step 2: Locate the decimal point. 0.2 x 0.7 0.14 1 decimal place 1 decimal place 2 decimal places

Example Find the product of 1.45 x 2.6.
Step 1: Multiply as with whole numbers. Step 2: Locate the decimal point.

Example Find the product of 1.02 x 3.6.
Step 1: Multiply as with whole numbers. Step 2: Locate the decimal point.

Multiplying using the Properties…
Use mental math to find 2 x x 0.5 We know that 2 x 0.5 will give us 1 and then the product of 1 and is 2 x x 0.5 = 2 x 0.5 x 4.097 Commutative Property Associative Property = (2 x 0.5) x 4.097 = 1 x 4.097 Simplify = 4.097 Identity Property

Example Use mental math to find the product of 1.09 x 23.6 x 0.

Example Use mental math to find the product of 2.5 x 6.3 x 4.

Additional Problems 1. 1.45 x 2.6 2. 1.3 x 0.005 3. 41 x 7.5