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Warm Up

Warm Up. Problem of the Day. Lesson Presentation. Lesson Quizzes. Warm Up Estimate by rounding to the indicated place value. 1. 70.27 + 15.36; ones 2. 84.37 – 21.82; tenths Estimate each product or quotient. 3. 27.25  8.7 4. 44.52 ÷ 3.27. 85. 62.6. 270. 15. Problem of the Day

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Warm Up

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  1. Warm Up Problem of the Day Lesson Presentation Lesson Quizzes

  2. Warm Up Estimate by rounding to the indicated place value. 1.70.27 + 15.36; ones 2. 84.37 – 21.82; tenths Estimate each product or quotient. 3. 27.25  8.7 4. 44.52 ÷ 3.27 85 62.6 270 15

  3. Problem of the Day Find a three-digit number that rounds to 440 and includes a digit that is the quotient of 24 and 3. Is there more than one possible answer? Explain your thinking. 438; no; the numbers that round to 440 are 435-444, 24 divided by 3 is 8, and 438 is the only number with 8 as a digit.

  4. Learn to add and subtract decimals.

  5. Helpful Hint Estimating before you add or subtract will help you check whether your answer is reasonable.

  6. At the 2004 U.S. Gymnastics Championships, Carly Patterson and Courtney Kupets tied for the All-Around title. To find the total number of points, you add all of the scores.

  7. Estimate by rounding to the nearest whole number. The total is about 28 points. Additional Example 1A: Sports Application What was Carly Patterson’s total for the events other than the floor exercise? Find the sum of 9.7, 9.3, and 9.45. 9.7 + 9.3 + 9.45 10 + 9 + 9 = 28

  8. Align the decimal points. Use zeros as placeholders. Add. Then place the decimal point. Additional Example 1A Continued Add. 9.70 9.30 +9.45 28.45 Since 28.45 is close to the estimate of 28, the answer is reasonable. Carly Patterson’s total for the events other than the floor exercise was 28.45.

  9. Align the decimal points. Use zeros as placeholders. Subtract. Then place the decimal point. Additional Example 1B: Sports Application How many more points did Carly need on the vault to have a perfect score of 10? Find the difference between 10 and 9.3. 10.0 -9.3 0.7 Carly needed another 0.7 of a point to have a perfect score.

  10. Estimate by rounding to the nearest whole number. The total is about 29 points. Check It Out: Example 1A What was Carly Patterson’s total for the events other than the vault exercise? Find the sum of 9.7, 9.7, and 9.45. 9.7 + 9.7 + 9.45 10 + 10 + 9 = 29

  11. Align the decimal points. Use zeros as placeholders. Add. Then place the decimal point. Check It Out: Example 1A Continued Add 9.700 9.700 +9.450 28.850 Since 28.850 is close to the estimate of 29, the answer is reasonable. Carly Patterson’s total for the events other than the vault exercise was 28.85.

  12. Align the decimal points. Use zeros as placeholders. Subtract. Then place the decimal point. Check It Out: Example 1B How many more points did Carly need on the uneven bars to have a perfect score of 10? Find the difference between 10 and 9.45. 10.00 -9.45 0.55 Carly needed another 0.55 of a point to have a perfect score.

  13. Think: 0.8 + 0.2 = 1. Think: What number added to 0.7 is 1? 0.7 + 0.3 = 1 So 1 – 0.7 = 0.3 Additional Example 2: Using Mental Math to Add and Subtract Decimals Find each sum or difference. A. 1.8 + 0.2 B. 4 – 0.7 1.8 + 0.2 = 2.0 4 – 0.7 = 3.3

  14. Think: 0.6 + 0.4 = 1. Think: What number added to 0.3 is 1? 0.3 + 0.7 = 1 So 1 – 0.3 = 0.7 Check It Out: Example 2 Find each sum or difference. A. 1.6 + 0.4 B. 6 – 0.3 1.6 + 0.4 = 2.0 6 – 0.3 = 5.7

  15. Substitute 3.8 for x. Align the decimal points. Use a zero as a placeholder. Subtract. Place the decimal point. Additional Example 3A: Evaluating Decimal Expressions Evaluate 6.73 – x for each value of x. x = 3.8 6.73 – x 6.73 –3.8 6.73 – 3.80 2.93

  16. Helpful Hint You can place any number of zeros at the end of a decimal number without changing its value.

  17. Substitute 2.9765 for x. Align the decimal points. Use zeros as placeholders. Subtract. Place the decimal point. Additional Example 3B: Evaluating Decimal Expressions Evaluate 6.73 – x for each value of x. x = 2.9765 6.73 – x 6.73 – 2.9765 6.7300 –2.9765 3.7535

  18. Substitute 3.8 for x. Align the decimal points. Use a zero as a placeholder. Subtract. Place the decimal point. Check It Out: Example 3A Evaluate 7.58 – x for each value of x. x = 3.8 7.58 – x 7.58 – 3.8 7.58 –3.80 3.78

  19. Substitute 2.9765 for x. Align the decimal points. Use zeros as placeholders. Subtract. Place the decimal point. Check It Out: Example 3B Evaluate 8.17 – x for each value of x. x = 2.9765 8.17 – x 8.17 – 2.9765 8.1700 – 2.9765 5.1935

  20. Lesson Quizzes Standard Lesson Quiz Lesson Quiz for Student Response Systems

  21. Lesson Quiz Find each sum or difference. 1. 8.3 + 2.7 2. 9.7 – 4 3. 22.6 + 8.4 4. Evaluate 12.76 – x for x = 8.41. 5. During an ice-skating competition, Dawn received the following scores: 4.8, 5.2, 5.4. What was Dawn’s total score? 11 5.7 31 4.35 15.4

  22. Lesson Quiz for Student Response Systems 1. Identify the sum. 9.4 + 3.6 A. 12.8 B. 13 C. 14 D. 15.5

  23. Lesson Quiz for Student Response Systems 2. Identify the difference. 12.6 – 6 A. 5 B. 5.6 C. 6 D. 6.6

  24. Lesson Quiz for Student Response Systems 3. Identify the sum. 19.91 + 9.09 A. 27 B. 28 C. 29 D. 30

  25. Lesson Quiz for Student Response Systems 4. During an gymnastics competition, Jack scored the following points: 9.2, 7.8, and 6.5. What was Jack’s total score? A. 21.5 points B. 22.5 points C. 23.5 points D. 24.5 points

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