1. Adding and Subtracting Decimals MAX Strategy Paired Reading Both students will read the problem and answer. When both partners are done reading one partner will use the whiteboard and marker to explain how to solve the problem. The partner must show the steps and tell the other partner the steps as they work it out. Then we will switch.

2. Adding and Subtracting Decimals I can fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation.

3. Adding and Subtracting Decimals Carly Patterson’s Preliminary Scores EventPoints Floor exercise9.7 Balance beam9.7 Vault9.3 Uneven bars9.45 At the 2004 U.S. Gymnastics Championships, Carly Patterson and Courtney Kupets tied for the All-Around title. To find the total number of points, you add all of the scores.

4. Adding and Subtracting Decimals What was Carly Patterson’s total for the events other than the floor exercise? 9.70 9.30 +9.45 28.45 Align the decimal points.Use zeros as placeholders.Add. Then place the decimal point. Since 28.45 is close to the estimate of 28, the answer is reasonable. Carly Patterson’s total for the events other than the floor exercise was 28.45. Find the sum of 9.7, 9.3, and 9.45.

5. Adding and Subtracting Decimals Additional Example 1B: Sports Application How many more points did Carly need on the vault to have a perfect score of 10? 10.0 -9.3 0.7 Align the decimal points.Use zeros as placeholders.Subtract. Then place the decimal point. Carly needed another 0.7 of a point to have a perfect score. Find the difference between 10 and 9.3.

6. Adding and Subtracting Decimals What was Carly Patterson’s total for the events other than the vault exercise? 9.700 +9.450 28.850 Align the decimal points.Use zeros as placeholders.Add. Then place the decimal point. Since 28.850 is close to the estimate of 29, the answer is reasonable. Carly Patterson’s total for the events other than the vault exercise was 28.85. Find the sum of 9.7, 9.7, and 9.45.

7. Adding and Subtracting Decimals Check It Out: Example 1B How many more points did Carly need on the uneven bars to have a perfect score of 10? 10.00 -9.45 0.55 Align the decimal points.Use zeros as placeholders.Subtract. Then place the decimal point. Carly needed another 0.55 of a point to have a perfect score. Find the difference between 10 and 9.45.

8. Adding and Subtracting Decimals Additional Example 3A: Evaluating Decimal Expressions Evaluate 6.73 – x for each value of x. x = 3.8 Substitute 3.8 for x. 6.73 – x 6.73 – 3.8 6.73 Align the decimal points. – 3.80 Use a zero as a placeholder. 2.93 Subtract. Place the decimal point.

9. Adding and Subtracting Decimals You can place any number of zeros at the end of a decimal number without changing its value. Helpful Hint

10. Adding and Subtracting Decimals Additional Example 3B: Evaluating Decimal Expressions Evaluate 6.73 – x for each value of x. x = 2.9765 Substitute 2.9765 for x. 6.73 – x 6.73 – 2.9765 6.7300 Align the decimal points. –2.9765 Use zeros as placeholders. 3.7535 Subtract. Place the decimal point.

11. Adding and Subtracting Decimals Check It Out: Example 3A Evaluate 7.58 – x for each value of x. x = 3.8 Substitute 3.8 for x. 7.58 – x 7.58 – 3.8 7.58 Align the decimal points. –3.80 Use a zero as a placeholder. 3.78 Subtract. Place the decimal point.

12. Adding and Subtracting Decimals Check It Out: Example 3B Evaluate 8.17 – x for each value of x. x = 2.9765 Substitute 2.9765 for x. 8.17 – x 8.17 – 2.9765 8.1700 Align the decimal points. – 2.9765 Use zeros as placeholders. 5.1935 Subtract. Place the decimal point.

13. Adding and Subtracting Decimals Lesson Quiz Find each sum or difference. 1. 8.3 + 2.7 2. 9.7 – 4 3. 22.6 + 8.4 4. Evaluate 12.76 – x for x = 8.41. 5. During an ice-skating competition, Dawn received the following scores: 4.8, 5.2, 5.4. What was Dawn’s total score? 5.7 11 31 4.35 15.4