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Holt CA Course 1 4-8 Dividing Decimals Warm Up Warm Up California Standards California Standards Lesson Presentation Lesson PresentationPreview

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Holt CA Course 1 4-8 Dividing Decimals Warm Up Divide. 1. 24.5 ÷ 7 2. 50.4 ÷ 6 3. 19.2 ÷ (–2) 4. 128.1 ÷ 21 3.5 8.4 –9.6 6.1

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Holt CA Course 1 4-8 Dividing Decimals Extension of NS2.3 Solve addition, subtraction, multiplication, and division problems, including those arising in concrete situations, that use positive and negative integers and combinations of these operations. (Review of 5 th grade NS 2.1) California Standards

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Holt CA Course 1 4-8 Dividing Decimals You can use a grid to model 0.6 0.3. Circle groups of 0.3 and count the number of groups. There are 2 groups of 0.3 in 0.6, so 0.6 ÷ 0.3 = 2. 10 colums of 10 = 100 squares 6 colums shaded = 6/10 =.6 3 colums grouped = 3/10 =.3

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Holt CA Course 1 4-8 Dividing Decimals When you divide two numbers, you can multiply both numbers by the same power of ten without changing the final answer. Multiply both 0.6 and 0.3 by 10: 0.6 10 = 6 and 0.3 10 = 3 0.6 ÷ 0.3 = 2 and 6 ÷ 3 = 2 By multiplying both numbers by the same power of ten, you can make the divisor an integer. Dividing by an integer is much easier than dividing by a decimal.

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Holt CA Course 1 4-8 Dividing Decimals Divide. Additional Example 1A: Dividing Decimals by Decimals 8.28 ÷ 4.6 ) 82.8 46 1. 46 – 36 8 –36 8 Multiply both numbers by 10 to make the divisor an integer. Divide as with whole numbers. 0 Multiply both numbers by the least power of ten that will make the divisor an integer. Helpful Hint 8.28 ÷ 4.6 8

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Holt CA Course 1 4-8 Dividing Decimals Divide. Additional Example 1B: Dividing Decimals by Decimals 18.48 ÷ (–1.75) Multiply both numbers by 100 to make the divisor an integer. ) 175 1848. 00 Use zeros as placeholders. Divide as with whole numbers. 1 –175 98 0 0.5 –87 5 10 50 –10 50 0 18.48 ÷ (–1.75) = –10.56 6 The signs are different.

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Holt CA Course 1 4-8 Dividing Decimals Check It Out! Example 1A Divide. 6.45 ÷ 0.5 ) 64.5 5 1 5 – 14 –10 6.45 ÷ 0.5 2 4 5. 9 –4 5 0 Multiply both numbers by 10 to make the divisor an integer. Divide as with whole numbers.

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Holt CA Course 1 4-8 Dividing Decimals Divide. 16.48 ÷ (–2.06) ) 1,648 206 8 –1 648 16.48 ÷ (–2.06) = –8 Multiply both numbers by 100 to make the divisor an integer. Divide as with whole numbers. 0 Check It Out! Example 1B The signs are different.

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Holt CA Course 1 4-8 Dividing Decimals Divide. Estimate to check whether each answer is reasonable. Additional Example 2A: Dividing Integers by Decimals 4 ÷ 1.25 4.00 ÷ 1.25 Multiply both numbers by 100. ) 125 400.0.0 Use zero as a placeholder. 3 –375 25 0 –25 0 0 Divide as with whole numbers. Estimate 4 ÷ 1 = 4 The answer is reasonable.. 2

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Holt CA Course 1 4-8 Dividing Decimals Divide. Estimate to check whether each answer is reasonable. Additional Example 2B: Dividing Integers by Decimals –24 ÷ (–2.5) –24.0 ÷ (–2.5) Multiply both numbers by 10. ) 25 240 9 – 225 15.. 0 0 6 – 15 0 0 Estimate –24 ÷ (–3) = 8 The answer is reasonable. Divide as with whole numbers.

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Holt CA Course 1 4-8 Dividing Decimals Divide. Estimate to check whether each answer is reasonable. Check It Out! Example 2A 6 ÷ 1.25 6.00 ÷ 1.25 Multiply both numbers by 100. ) 125 600.0.0 Use zero as a placeholder. 4 –500 100 0 –100 0 0 Divide as with whole numbers. Estimate 6 ÷ 1 = 6 The answer is reasonable.. 8

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Holt CA Course 1 4-8 Dividing Decimals Divide. Estimate to check whether each answer is Reasonable. Check It Out! Example 2B –22 ÷ (–2.5) –22.0 ÷ (–2.5) Multiply both numbers by 10. ) 25 220 8 –200 20.. 0 0 8 –20 0 0 Estimate –21 ÷ (–3) = 7 The answer is reasonable. Divide as with whole numbers.

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Holt CA Course 1 4-8 Dividing Decimals Eric paid $229.25 to rent a car. The fee to rent the car was $32.75 per day. For how long did Eric rent the car? Additional Example 3: Transportation Application 229.25 ÷ 32.75Multiply both numbers by 100. ) 3,275 22,925 Divide as with whole numbers. 7 –22,925 0 Eric rented the car for 7 days.

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Holt CA Course 1 4-8 Dividing Decimals Check It Out! Example 3 Jace took a trip in which he drove 350 miles. During the trip his truck used 12.5 gallons of gas. What was his truck’s gas mileage? 350.0 ÷ 12.5 Multiply both numbers by 10. ) 125 3500 Divide as with whole numbers. 2 –250 100 8 0 –1000 0 The gas mileage was 28 miles per gallon. To calculate miles per gallon, divide the number of miles driven by the number of gallons of gas used. Helpful Hint

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Holt CA Course 1 4-8 Dividing Decimals Lesson Quiz Divide. Estimate to check whether each answer is reasonable. 1. 78.2 ÷ 0.04 2. –9.72 ÷ 2.7 3. 18.88 ÷ 1.6 4. 19.5 ÷ 3.25 5. Jordan used 32.46 gallons of gas to drive his van 584.28 miles. How many miles did Jordan get per gallon? –3.6 1,995 11.8 6 18

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