Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 5.2 Adding and Subtracting Decimals

Martin-Gay, Prealgebra, 6ed 22 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 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, Prealgebra, 6ed 33 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Recall that 0s may be inserted to the right of the decimal point after the last digit without changing the value of the decimal. This may be used to help line up place values when adding or subtracting decimals. becomes 85  becomes  two 0s inserted Helpful Hint

Martin-Gay, Prealgebra, 6ed 44 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Don’t forget that the decimal point in a whole number is after the last digit. Helpful Hint

Martin-Gay, Prealgebra, 6ed 55 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Estimating sums, differences, products, and quotients of decimal numbers is an important skill whether you use a calculator or perform decimal operations by hand. Estimating Operations on Decimals

Martin-Gay, Prealgebra, 6ed 66 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Add Estimating When Adding Decimals Exact Estimate rounds to This is a reasonable answer.

Martin-Gay, Prealgebra, 6ed 77 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. When rounding to check a calculation, you may want to round the numbers to a place value of your choosing so that your estimates are easy to compute mentally. Helpful Hint

Martin-Gay, Prealgebra, 6ed 88 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Evaluate x + y for x = 5.5 and y = 2.8. Evaluating with Decimals x + y = ( ) + ( ) Replace x with 5.5 and y with 2.8 in x + y = 8.3