5.3 Adding and Subtracting Signed Decimal Numbers Chapter 5 Rational Numbers: Positive and Negative Decimals

5.3 Adding and Subtracting Signed Decimal Numbers Objectives Add and subtract positive decimals. Add and subtract negative decimals. Estimate the answer when adding or subtracting decimals. Copyright © 2010 Pearson Education, Inc. All rights reserved.

Objective 1: Add and subtract positive decimals. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 4

Objective 1: Add and subtract positive decimals. Example Find the sum of 16.92 and 48.34. Step 1 Write the numbers in columns with the decimal points lined up. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 5

Objective 1: Add and subtract positive decimals. Example (continued) Step 2 Add as if these were whole numbers. Step 3 Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 6

Objective 1: Add and subtract positive decimals. Example Find the sum 5.897 + 4.632 + 12.174. Write the numbers in columns with the decimal points lined up. Then add. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 7

Objective 1: Add and subtract positive decimals. Example Find the sum 7.3 + 0.85. Write a 0 in the hundredths place in 7.3, so it has two decimal places also. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 8

Objective 1: Add and subtract positive decimals. Example Find the sum 6.42 + 9 + 2.576. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 9

Objective 1: Add and subtract positive decimals. Example Find the difference of 16.92 and 48.34. Step 1 Step 2 Step 3 Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 10

Objective 1: Add and subtract positive decimals. Example Find 146.35 minus 58.98. Regrouping is needed in this problem. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 11

Objective 1: Add and subtract positive decimals. Example Subtract 16.5 from 28.362. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 12

Objective 1: Add and subtract positive decimals. Example Find 12 less 5.83. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 13

Objective 2: Add and subtract negative decimals. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 14

Objective 2: Add and subtract negative decimals. Example Find the sum of –3.7 + (–16). Both addends are negative, so the sum will be negative. Add the absolute values. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 15

Objective 2: Add and subtract negative decimals. Example Find the sum of –5.23 + 0.792. The addends have different signs. Find absolute values of each and subtract the smaller absolute value from the larger. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 16

Objective 2: Add and subtract negative decimals. Example Find the difference of 4.3 – 12.73. –12.73 has the larger absolute value and is negative, so the answer will be negative. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 17

Objective 2: Add and subtract negative decimals. Example Find the difference of –4.3 – (–4.8). 4.8 has the larger absolute value and is positive, so the answer will be positive. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 18

Objective 2: Add and subtract negative decimals. Example Find the difference 14.2 – (1.69 + 0.48). Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 19

Objective 3: Estimate the answer when adding or subtracting decimals. Estimate the sum of 194.2 and 6.825 using front end rounding. Then find the exact answer. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 20

Objective 3: Estimate the answer when adding or subtracting decimals. Subtract $13.78 from $69.42 using front end rounding. Then find the exact answer. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 21

Objective 3: Estimate the answer when adding or subtracting decimals. Subtract –1.861 – 7.3 using front end rounding. Then find the exact answer. Example Estimate: Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 22

Objective 3: Estimate the answer when adding or subtracting decimals. Subtract –1.861 – 7.3 using front end rounding. Then find the exact answer. Example Exact: The answer will be negative because both numbers are negative. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.3 - 23