 # Monday, Oct 7 Lesson 3.1 Add and Subtract Decimals.

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Monday, Oct 7 Lesson 3.1 Add and Subtract Decimals

Objective: To understand how to add and subtract decimals.

Add and Subtract Decimals At the end of this lesson you should be able to answer the following question. How is estimation helpful when adding and subtracting decimals?

Add and Subtract Decimals To add and subtract decimals, line up the decimal point and then add or subtract as normal.

Add and Subtract Decimals Find the sum of 23.1 and 5.8. First round the numbers to the nearest whole number to get an estimate. What does 23.1 round to? Digits from 0 to 4 round down and digits from 5-9 round up.

Add and Subtract Decimals Find the sum of 23.1 and 5.8. First round the numbers to the nearest whole number to get an estimate. What does 23.1 round to? 23 What does 5.8 round to?

Add and Subtract Decimals Find the sum of 23.1 and 5.8. First round the numbers to the nearest whole number to get an estimate. What does 23.1 round to? 23 What does 5.8 round to? 6

Add and Subtract Decimals Find the sum of 23.1 and 5.8. First round the numbers to the nearest whole number to get an estimate. 23 + 6 = 29, so 23.1 + 5.8 ≈ 29

Add and Subtract Decimals Find the sum of 23.1 and 5.8. To add and subtract decimals. Step 1 – Stack the numbers and line up the decimal point. 23.1 + 5.8

Add and Subtract Decimals Find the sum of 23.1 and 5.8. To add and subtract decimals. Step 2 – Add or subtract the digits. You may need to annex zeros. 23.1 + 5.8 2 8 9

Add and Subtract Decimals Find the sum of 23.1 and 5.8. To add and subtract decimals. Step 3 – Bring the decimal point down. 23.1 + 5.8 28.9

Add and Subtract Decimals Find the sum of 23.1 and 5.8. To add and subtract decimals. Step 3 – Bring the decimal point down. 23.1 + 5.8 28.9 Is this a reasonable answer?

Add and Subtract Decimals Find the sum of 23.1 and 5.8. To add and subtract decimals. Step 3 – Bring the decimal point down. 23.1 + 5.8 28.9 Is this a reasonable answer? 28.9 ≈ 29

Add and Subtract Decimals Find the sum of 29.6 and 14.7. What is the estimate?

Add and Subtract Decimals Find the sum of 29.6 and 14.7. What is the estimate? 30 + 15 ≈ 45

Add and Subtract Decimals Find the sum of 29.6 and 14.7. What is the actual sum?

Add and Subtract Decimals Find the sum of 29.6 and 14.7. What is the actual sum? 29.6 +14.7 44.3 Is this a reasonable answer?

Add and Subtract Decimals Find the sum of 29.6 and 14.7. What is the actual sum? 29.6 +14.7 44.3 Is this a reasonable answer? 44.3 ≈ 45

Add and Subtract Decimals Find the estimate and actual sum of 54.7 and 21.4. (Do this on your own)

Add and Subtract Decimals Find the estimate and actual sum of 54.7 and 21.4. Estimate 55 + 21 = 76

Add and Subtract Decimals Find the estimate and actual sum of 54.7 and 21.4. Estimate 55 + 21 = 76 54.7 +21.4 76.1 Is this a reasonable answer?

Add and Subtract Decimals Find the estimate and actual sum of 54.7 and 21.4. Estimate 55 + 21 = 76 54.7 +21.4 76.1 Is this a reasonable answer? 76.1 ≈ 76

Add and Subtract Decimals Find the estimate and actual difference of 5.774 and 2.371. (Do this on your own)

Add and Subtract Decimals Find the estimate and actual difference of 5.774 and 2.371. Estimate 6 - 2 = 4

Add and Subtract Decimals Find the estimate and actual difference of 5.774 and 2.371. Estimate 6 - 2 = 4 5.774 -2.371 3.403 Is this a reasonable answer?

Add and Subtract Decimals Find the estimate and actual difference of 5.774 and 2.371. Estimate 6 - 2 = 4 5.774 -2.371 3.403 Is this a reasonable answer? 3.403 ≈ 4

Add and Subtract Decimals Find the estimate and actual difference of 6 and 4.78. (Do this on your own)

Add and Subtract Decimals Find the estimate and actual difference of 6 and 4.78. Estimate 6 - 5 = 1

Add and Subtract Decimals Find the estimate and actual difference of 6 and 4.78. Estimate 6 - 5 = 1 6.00 Annex zeros so each number -4.78 has the same amount of decimals. 1.22 Is this a reasonable answer?

Add and Subtract Decimals Find the estimate and actual difference of 6 and 4.78. Estimate 6 - 5 = 1 6.00 -4.78 1.22 Is this a reasonable answer? 1.22 ≈ 1

Add and Subtract Decimals Find the estimate and actual difference of 9.543 and 3.671. (Do this on your own)

Add and Subtract Decimals Find the estimate and actual difference of 9.543 and 3.671. Estimate 10 - 4 = 6

Add and Subtract Decimals Find the estimate and actual difference of 9.543 and 3.671. Estimate 10 - 4 = 6 9.543 -3.671 5.872 Is this a reasonable answer?

Add and Subtract Decimals Find the estimate and actual difference of 9.543 and 3.671. Estimate 10 - 4 = 6 9.543 -3.671 5.872 Is this a reasonable answer? 5.872 ≈ 6

Add and Subtract Decimals Reagan is creating a video. The first video clip was 22.36 minutes long. The second video clip was 17.03 minutes long. What is the total length of the video? (Do this on your own)

Add and Subtract Decimals Reagan is creating a video. The first video clip was 22.36 minutes long. The second video clip was 17.03 minutes long. What is the total length of the video? Estimate 22 +17 = 39

Add and Subtract Decimals Reagan is creating a video. The first video clip was 22.36 minutes long. The second video clip was 17.03 minutes long. What is the total length of the video? Estimate 22 +17 = 39 22.36 +17.03 39.39 Is this a reasonable answer?

Add and Subtract Decimals Reagan is creating a video. The first video clip was 22.36 minutes long. The second video clip was 17.03 minutes long. What is the total length of the video? Estimate 22 +17 = 39 22.36 +17.03 39.39 Is this a reasonable answer? 39.39 ≈ 39

Add and Subtract Decimals Complete the Guided Practice on page 180. When complete bring to the desk and show Mr. Avery. Agenda Notes Homework –Homework Practice 3-1 Due Tuesday, Oct 8 Mid-Chapter 3 Quiz –Thursday, Oct 10