9 ADDING AND SUBTRACTING DECIMALS Helpful Hint Estimating

#9 ADDING AND SUBTRACTING DECIMALS

Helpful Hint Estimating before you add or subtract will help you check whether your answer is reasonable.

At the 2004 U. S. Gymnastics Championships, Carly Patterson and Courtney Kupets tied for the All-Around title. Carly Patterson’s Preliminary Scores Event Points Floor exercise 9. 7 Balance beam 9. 7 Vault 9. 3 Uneven bars 9. 45 To find the total number of points, you add all of the scores.

Example 1 : Real-World Application What was Carly Patterson’s total for the events other than the floor exercise?

Example 2: Real-World Application How many more points did Carly need on the vault to have a perfect score of 10?

Example 3 What was Carly Patterson’s total for the events other than the vault exercise?

Example 4 How many more points did Carly need on the uneven bars to have a perfect score of 10? Find the difference between 10 and 9. 45.

Example 5: Using Mental Math to Add and Subtract Decimals Find each sum or difference. A. 1. 8 + 0. 2 B. 4 – 0. 7

Example 6 Find each sum or difference. A. 1. 6 + 0. 4 B. 6 – 0. 3

Example 8: Evaluating Decimal Expressions Evaluate 6. 73 – x for each value of x. x = 3. 8

Helpful Hint You can place any number of zeros at the end of a decimal number without changing its value.

Example 9: Evaluating Decimal Expressions Evaluate 6. 73 – x for each value of x. x = 2. 9765

Example 10 Evaluate 8. 17 – x for each value of x. x = 2. 9765