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3-8

3-8. Dividing by Decimals. Course 1. Warm Up. Problem of the Day. Lesson Presentation. 3-8. Dividing by Decimals. Course 1. Warm Up Divide. 1. 4.8 ÷ 2 2. 16.1 ÷ 7 3. 0.36 ÷ 3 4. 25.28 ÷ 4 5. 6.25 ÷ 5. 2.4. 2.3. 0.12. 6.32. 1.25. 3-8. Dividing by Decimals. 3. 1. 1.5.

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3-8

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  1. 3-8 Dividing by Decimals Course 1 Warm Up Problem of the Day Lesson Presentation

  2. 3-8 Dividing by Decimals Course 1 Warm Up Divide. 1.4.8 ÷ 2 2. 16.1 ÷ 7 3. 0.36 ÷ 3 4. 25.28 ÷ 4 5. 6.25 ÷ 5 2.4 2.3 0.12 6.32 1.25

  3. 3-8 Dividing by Decimals 3 1 1.5 2.25 0.75 9 Course 1 Problem of the Day In the following magic square, 3.375 is the product of the numbers in every row, column, and diagonal. Fill in the missing numbers.

  4. 3-8 Dividing by Decimals Course 1 Learn to divide whole numbers and decimals by decimals.

  5. 3-8 Dividing by Decimals Helpful Hint Multiplying the divisor and the dividend by the same number does not change the quotient. 42 ÷ 6 = 7 10  10 420 ÷ 60 = 7  10  10 4,200 ÷ 600 = 7 Course 1

  6. 3-8 Dividing by Decimals Multiply the divisor and dividend by the same power of ten. There is one decimal place in the divisor. Multiply by 101, or 10. Think: 1.3 x 10 = 13 5.2 x 10 = 52 Divide. Course 1 Additional Example 1A: Dividing a Decimal by a Decimal Find each quotient. A. 5.2 ÷ 1.3 1.3 5.2 4 13 52 –52 0

  7. 3-8 Dividing by Decimals 36 6,130.000 Think: 0.36 x 100 = 36 61.3 x 100 = 6,130 Make the divisor a whole number by multiplying the divisor and dividend by 102, or 100. Course 1 Additional Example 1B: Dividing a Decimal by a Decimal B. 61.3 ÷ 0.36 0.36 61.3

  8. 3-8 Dividing by Decimals __ When a repeating pattern occurs, show three dots or draw a bar over the repeating part of the quotient. Divide. 170.277… = 170.27 Course 1 Additional Example 1B Continued 0 .2 1 7 7 7 36 6,130.000 -36 253 252 10 -0 100 -72 280 -252 280 -252 28

  9. 3-8 Dividing by Decimals 1 Multiply the divisor and dividend by the same power of ten. There is one decimal place in the divisor. Multiply by 10 , or 10. Think: 1.2 x 10 = 12 4.8 x 10 = 48 Divide. Course 1 Try This: Example 1A Find each quotient. A. 4.8 ÷ 1.2 1.2 4.8 4 12 48 -48 0

  10. 3-8 Dividing by Decimals 24 5120.000 Think: 0.24 x 100 = 24 51.2 x 100 = 5,120 Make the divisor a whole number by multiplying the divisor and dividend by 102, or 100. Course 1 Try This: Example 1B B. 51.2 ÷ 0.24 0.24 51.2

  11. 3-8 Dividing by Decimals __ Divide. When a repeating pattern occurs, show three dots or draw a bar over the repeating part of the quotient. 213.33… = 213.33 Course 1 Try This: Example 1B Continued 3 2 .3 1 3 24 5,120.00 -48 32 24 80 -72 80 -72 80 -72 8

  12. 3-8 Dividing by Decimals 1 Understand the Problem Course 1 Additional Example 2: Problem Solving Application After driving 216.3 miles, the Yorks used 10.5 gallons of gas. On average, how many miles did they drive per gallon of gas? The answer will be the average number of miles per gallon. List the important information: They drove 216.3 miles. They used 10.5 gallons of gas.

  13. 3-8 Dividing by Decimals 3 Solve Make a Plan 2 Multiply the divisor and dividend by 10. Think: 10.5 x 10 = 105 216.3 x 10 = 2,163 Place the decimal point in the quotient. Divide. Course 1 Solve a simpler problem by replacing the decimals in the problem with whole numbers. If they drove 10 miles using 2 gallons of gas, they averaged 5 miles per gallon. You need to divide miles by gallons to solve the problem. 10.5 216.3 The York family averaged 20.6 miles per gallon.

  14. 3-8 Dividing by Decimals Use compatible numbers to estimate the quotient. 216.3 ÷ 10.5 220 ÷ 11 =20 The answer is reasonable since 20.6 is close to the estimate of 20. 4 Look Back Course 1

  15. 3-8 Dividing by Decimals 1 Understand the Problem Course 1 Try This: Example 2 After driving 191.1 miles, the Changs used 10.5 gallons of gas. On average, how many miles did they drive per gallon of gas? The answer will be the average number of miles per gallon. List the important information: They drove 191.1 miles. They used 10.5 gallons of gas.

  16. 3-8 Dividing by Decimals 3 Solve Make a Plan 2 Multiply the divisor and dividend by 10. Think: 10.5 x 10 = 105 191.1 x 10 = 1,911 Place the decimal point in the quotient. Divide. Course 1 Solve a simpler problem by replacing the decimals in the problem with whole numbers. If they drove 10 miles using 2 gallons of gas, they averaged 5 miles per gallon. You need to divide miles by gallons to solve the problem. 10.5 191.1 The York family averaged 18.2 miles per gallon.

  17. 3-8 Dividing by Decimals Use compatible numbers to estimate the quotient. 191.1 ÷ 10.5 190 ÷ 10 = 19 The answer is reasonable since 18.2 is close to the estimate of 19. 4 Look Back Course 1

  18. 3-8 Dividing by Decimals Course 1 Insert Lesson Title Here Lesson Quiz Find each quotient. 1. 49 ÷ 0.7 2. 21.63 ÷ 2.1 3. 38.43 ÷ 6.1 4. 16.9 ÷ 5.2 5. John spent $13.44 renting 4 videos for the weekend. What was the cost per video? 70 10.3 6.3 3.25 $3.36

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