Download 6.4 Operations with Decimals

Procedure for Adding and Subtracting Rational Numbers Represented by Decimals
y Align the place‐value positions by aligning the Section 6.4
Operations with Decimals
Multiplying Rational Numbers in Decimal Form
Examples
1) 25.42 + 3.9
decimal points and apply the algorithms for addition or subtraction of whole numbers.
addition or subtraction of whole numbers
y Demonstrate the Standard Procedure, then Verify using Fractions. (see page 344) y Note: For subtraction, write each number with the same denominator. Add zeros as necessary.
2) 47.6 – 5.834
y Multiply factors as if they are whole numbers, then place the decimal point in the appropriate place in the product.
y The product of a factor with m places to the right of the ones place and a factor with n places to the right of the ones place will have m + n decimal places to the right of the ones place.
y Verify using fractions .
Procedure for Dividing Rational Numbers in Decimal Form
Examples
3) 6.14 x 1.3
4) –0.85 x 2.9
y Based on the Fundamental Law of Fractions
(Creating equivalent fractions)
y Consider 0.125 ÷
5 0.055
5) Find the product of 2.75 x 0.2 using the standard procedure for multiplying decimals. = 0.125 (100) ÷ 0.05 (100)
= 12.5 ÷ 5
= 2.5
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Consider 0.125 ÷ 0.05 again.
y How would we solve this using the standard Modeling with Decimals
y Using base‐ten blocks. Let 1 flat = 1 and 1 long = 1/10
algorithm for division?
y Using a number line or metric ruler.
Divide each unit into tenths, etc.
Divide each unit into tenths etc
y How could we check our answer?
y Using an area model.
Let one square = 1 and divide into tenths.
Modeling Examples
y From page 331 in textbook:
1c) Model 1.6 + 1.5 using base‐ten blocks.
2b) Model 0.6 –
)
0.3 using a number line 3
g
(or metric ruler).
3a) Model 0.6 x 0.5 using an area model.
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