1 / 19

3-3

3-3. Adding and Subtracting Decimals. Course 1. Warm Up. Problem of the Day. Lesson Presentation. 3-3. Adding and Subtracting Decimals. Course 1. Warm Up Estimate by rounding to the indicated place value. 1. 70.27 + 15.36; ones 2. 84.37 – 21.82; tenths

david-wilcox
Download Presentation

3-3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 3-3 Adding and Subtracting Decimals Course 1 Warm Up Problem of the Day Lesson Presentation

  2. 3-3 Adding and Subtracting Decimals Course 1 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. 3-3 Adding and Subtracting Decimals Course 1 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. 3-3 Adding and Subtracting Decimals Course 1 Learn to add and subtract decimals.

  5. 3-3 Adding and Subtracting Decimals Helpful Hint Estimating before you add or subtract will help you check whether your answer is reasonable. Course 1

  6. 3-3 Adding and Subtracting Decimals Course 1 American gymnast Elise Ray won the 2000 U.S. Championships in the all-around, uneven bars, and floor-exercise events. To find the total number of points, you add all of the scores.

  7. 3-3 Adding and Subtracting Decimals Estimate by rounding to the nearest whole number. The total is about 29 points. Course 1 Additional Example 1A: Sports Application A. What was Elise Ray’s total for the events other than the floor exercise? Find the sum of 9.7, 9.425, and 9.85. 9.7 + 9.425 + 9.85 10 + 9 + 10 = 29

  8. 3-3 Adding and Subtracting Decimals Align the decimal points. Use zeros as placeholders. Add. Then place the decimal point. Course 1 Additional Example 1A Continued Add. 9.700 9.425 +9.850 28.975 Since 28.975 is close to the estimate of 29, the answer is reasonable. Elise Ray’s total for the events other than the floor exercise was 28.975.

  9. 3-3 Adding and Subtracting Decimals Align the decimal points. Use zeros as placeholders. Subtract. Then place the decimal point. Course 1 Additional Example 1B: Sports Application B. How many more points did Elise need on the vault to have a perfect score of 10? Find the difference between 10 and 9.425. 10.000 -9.425 0.575 Elise needed another 0.575 points to have a perfect score.

  10. 3-3 Adding and Subtracting Decimals Estimate by rounding to the nearest whole number. The total is about 30 points. Course 1 Try This: Example 1A A. What was Elise Ray’s total for the events other than the vault exercise? Find the sum of 9.8, 9.7, and 9.85. 9.8 + 9.7 + 9.85 10 + 10 + 10 = 30

  11. 3-3 Adding and Subtracting Decimals Align the decimal points. Use zeros as placeholders. Add. Then place the decimal point. Course 1 Try This: Example 1A Continued Add 9.800 9.700 +9.850 29.350 Since 29.350 is close to the estimate of 30, the answer is reasonable. Elise Ray’s total for the events other than the vault exercise was 29.350.

  12. 3-3 Adding and Subtracting Decimals Align the decimal points. Use zeros as placeholders. Subtract. Then place the decimal point. Course 1 Try This: Example 1B B. How many more points did Elise need on the uneven bars to have a perfect score of 1 Find the difference between 10 and 9.85. 10.00 -9.85 0.15 Elise needed another 0.15 points to have a perfect score.

  13. 3-3 Adding and Subtracting Decimals 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 Course 1 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 4 – 0.7 = 3.3

  14. 3-3 Adding and Subtracting Decimals 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 Course 1 Try This: 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. 3-3 Adding and Subtracting Decimals Substitute 3.8 for x. Align the decimal points. Use a zero as a placeholder. Subtract. Place the decimal point. Course 1 Additional Example 3A: Evaluating Decimal Expressions Evaluate 6.73 – x for each value of x. A. x = 3.8 6.73 – x 6.73 –3.8 6.73 – 3.80 2.93

  16. 3-3 Adding and Subtracting Decimals Substitute 2.9765 for x. Align the decimal points. Use a zero as a placeholder. Subtract. Place the decimal point. Course 1 Additional Example 3B: Evaluating Decimal Expressions Evaluate 6.73 – x for each value of x. B. x = 2.9765 6.73 – x 6.73 – 2.9765 6.7300 –2.9765 3.7535

  17. 3-3 Adding and Subtracting Decimals Substitute 3.8 for x. Align the decimal points. Use a zero as a placeholder. Subtract. Place the decimal point. Course 1 Try This: Example 3A Evaluate 7.58 – x for each value of x. A. x = 3.8 7.58 – x 7.58 – 3.8 7.58 –3.80 3.78

  18. 3-3 Adding and Subtracting Decimals Substitute 2.9765 for x. Align the decimal points. Use a zero as a placeholder. Subtract. Place the decimal point. Course 1 Try This: Example 3B Evaluate 8.17 – x for each value of x. B. x = 2.9765 8.17 – x 8.17 – 2.9765 8.1700 – 2.9765 5.1935

  19. 3-3 Adding and Subtracting Decimals Course 1 Insert Lesson Title Here 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

More Related