1. 3-4 Multiplying Decimals Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day Lesson Quizzes Lesson Quizzes

2. 3-4 Multiplying Decimals Warm Up Multiply. 27,840 754,400 38,060 120,700 14,112 62,760 1. 87  320 2. 943  800 3. 3,806  10 4. 1,207  100 5. 72  196 6. 120  523

3. 3-4 Multiplying Decimals Problem of the Day Carmen and Rita sold homemade oatmeal cookies. After 8 days, they had sales totaling $70. Each day, their sales were $0.50 higher than the previous day. What were their sales on the first day? $7.00

4. 3-4 Multiplying Decimals MA.6.A.1.2 Multiply…decimals efficiently. MA.6.A.1.3 Solve real-world problems involving multiplication…of…decimals. Also MA.6.A.1.1 Sunshine State Standards

5. 3-4 Multiplying Decimals Additional Example 1: Science Application Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 4 lb dumbbell weigh on the Moon? Multiply 4 by 0.17, since 1 pound on Earth is 0.17 pound on the Moon. 17  4 68 Multiply as you would with whole numbers. 4  0.17

6. 3-4 Multiplying Decimals Additional Example 1 Continued Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 4 lb dumbbell weigh on the Moon? 0.17  4 0.68 Place the decimal point by adding the number of decimal places in the numbers multiplied. A 4 lb dumbbell on Earth weighs 0.68 lb on the Moon. 2 decimal places + 0 decimal places 2 decimal places

7. 3-4 Multiplying Decimals Check It Out: Example 1 Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 7 lb dumbbell weigh on the Moon? 7 × 0.17 = 1.19 lb

8. 3-4 Multiplying Decimals You can use a decimal grid to model multiplication of decimals. Helpful Hint

9. 3-4 Multiplying Decimals Additional Example 2A: Multiplying a Decimal by a Decimal Find the product. 0.3  0.4 Multiply. Then place the decimal point. 0.3 0.4  1 decimal place + 1 decimal place2 decimal places 0.12

10. 3-4 Multiplying Decimals Additional Example 2B: Multiplying a Decimal by a Decimal 0.07  0.8 Multiply. Then place the decimal point. 0.07  0.8 2 decimal places + 1 decimal place3 decimal places; use a placeholder zero 0.056 Estimate the product. 0.8 is close to 1. 0.07  1 = 0.07 0.056 is close to the estimate of 0.07. The answer is reasonable.

11. 3-4 Multiplying Decimals Additional Example 2C: Multiplying a Decimal by a Decimal 1.34  2.5 Multiply. Then place the decimal point. 1.34 2.5  2 decimal places + 1 decimal place3 decimal places 670 Estimate the product. Round each factor to the nearest whole number. 1  3 = 3 3.350 is close to the estimate of 3. The answer is reasonable. 2680 3.350

12. 3-4 Multiplying Decimals Check It Out: Example 2 Find the product. 3.80 × 3.3 3.80 3.3  1140 11400 12.540 = 12.54

13. 3-4 Multiplying Decimals Additional Example 3A: Evaluating Decimal Expressions Evaluate 5x for the value of x. x = 3.062 3.062 5  3 decimal places + 0 decimal places3 decimal places 15.310 Substitute 3.062 for x. 5x = 5(3.062) These notations all mean multiply 3 times x. 3 x3x3(x) Remember!

14. 3-4 Multiplying Decimals Additional Example 3B: Evaluating Decimal Expressions Evaluate 5x for the value of x. x = 4.79 4.79 5  2 decimal places + 0 decimal places2 decimal places 23.95 Substitute 4.79 for x. 5x = 5(4.79)

15. 3-4 Multiplying Decimals Check It Out: Example 3 Evaluate 5x for the value of x. x = 6.22 5(6.22) = 31.10 = 31.1