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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 1 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. 2