Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Chapter 4 Decimals

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 4.3 Adding and Subtracting Decimals

Martin-Gay, Developmental Mathematics, 2e 33 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Adding and Subtracting Decimals Adding or Subtracting Decimals Step 1: Write the decimals so that the decimal points line up vertically. Step 2: Add or subtract as with whole numbers. Step 3: Place the decimal point in the sum or difference so that it lines up vertically with the decimal points in the problem.

Martin-Gay, Developmental Mathematics, 2e 44 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Adding Decimals StepExample Step 1: Write the decimals so that the decimal points line up vertically. Add: Step 2: Add or subtract as with whole numbers. Step 3: Place the decimal point in the sum or difference so that it lines up vertically with the decimal points in the problem.

Martin-Gay, Developmental Mathematics, 2e 55 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example Add: Insert one zero

Martin-Gay, Developmental Mathematics, 2e 66 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example Subtract: – 5.9 Insert decimal point and one zero

Martin-Gay, Developmental Mathematics, 2e 77 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example Subtract: 28 – 3.3 Insert decimal point and one zero 24.7 Line up decimal points Subtract.

Martin-Gay, Developmental Mathematics, 2e 88 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Estimating when Adding or Subtracting Decimals To help avoid errors, we can estimate to see if our answer is reasonable by rounding the given numbers and adding or subtracting. Example: 7.6 – 2.1 rounds to Exact Since the exact answer is close, it is reasonable.

Martin-Gay, Developmental Mathematics, 2e 99 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Example A pair of eyeglasses costs a total of $ The frames of the glasses are $ How much do the lenses of the eyeglasses cost? The lenses of the eyeglasses cost $