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Chapter 3, Section 3, Page 102

Chapter 3, Section 3, Page 102. “Adding & Subtracting Decimals”. Remember In this class Only use a. Warm Up Estimate by rounding to the indicated place value. 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.

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Chapter 3, Section 3, Page 102

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  1. Chapter 3, Section 3, Page 102 “Adding & Subtracting Decimals”

  2. Remember In this class Only use a

  3. Warm Up Estimate by rounding to the indicated place value. 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

  4. Sunshine State Standards MA.6.A.5.3Estimate the results of computations with…decimals…and judge the reasonableness of the results. AlsoReview ofMA.5.A.2.2

  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? First estimate 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 Then 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. Helpful Hint You can place any number of zeros at the end of a decimal number without changing its value.

  11. 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? First estimate the sum of 9.7, 9.7, and 9.45. 9.7 + 9.7 + 9.45 10 + 10 + 9 = 29

  12. Align the decimal points. Use zeros as placeholders. Add. Then place the decimal point. Check It Out: Example 1A Continued Then 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.

  13. 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.

  14. Think: 0.8 + 0.2 = 1. Think: 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

  15. Think: 0.6 + 0.4 = 1. Think: 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

  16. 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

  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. Now to practice! Click Here!

  21. Lesson Quizzes Standard Lesson Quiz Complete in your notebook ~

  22. 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

  23. HOMEWORK Class Periods 1, 4 & 7 Page 104, #14-29 Class Periods 2, 3 & 6 (Advanced) Page 100, 104, #14-29 & 36-39 on page 105

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