1. Adding and Subtracting Decimals Section 5.2

2. Adding or Subtracting Decimals Step 1. Write the decimals so that the decimal points line up vertically. Step 2. Add or subtract as for 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. 2 Martin-Gay, Prealgebra, 5ed

3. Helpful Hint 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  13.26 becomes 85.00  13.26 71.74 two 0s inserted 3

4. Helpful Hint Don’t forget that the decimal point in a whole number is after the last digit. 4 Martin-Gay, Prealgebra, 5ed

5. 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, 5ed

6. Add 23.8 + 32.1. Estimating When Adding Decimals Exact Estimate rounds to This is a reasonable answer. Martin-Gay, Prealgebra, 5ed

7. Helpful Hint 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. Martin-Gay, Prealgebra, 5ed

8. 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. 5.52.8 = 8.3 8 Martin-Gay, Prealgebra, 5ed