Multiplying Decimals Warm Up Problem of the Day

Multiplying Decimals Warm Up Problem of the Day Lesson Presentation Lesson Quizzes

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

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

Multiplying Decimals Learn to multiply decimals by whole numbers and by decimals.

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? 4 0. 17 17 4 68 Multiply 4 by 0. 17, since 1 pound on Earth is 0. 17 pound on the Moon. Multiply as you would with whole numbers.

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? Place the decimal point by adding the number of decimal places in the numbers multiplied. 0. 17 4 0. 68 2 decimal places + 0 decimal places 2 decimal places A 4 lb dumbbell on Earth weighs 0. 68 lb on the Moon.

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 17 7 119 Multiply 7 by 0. 17, since 1 pound on Earth is 0. 17 pound on the Moon. Multiply as you would with whole numbers.

Multiplying Decimals Check It Out: Example 1 Continued 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? Place the decimal point by adding the number of decimal places in the numbers multiplied. 0. 17 7 1. 19 2 decimal places + 0 decimal places 2 decimal places A 7 lb dumbbell on Earth weighs 1. 19 lb on the Moon.

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

Multiplying Decimals Additional Example 2 A: Multiplying a Decimal by a Decimal Find the product. 0. 3 0. 4 Multiply. Then place the decimal point. 0. 3 1 decimal place 0. 4 + 1 decimal place 0. 12 2 decimal places

Multiplying Decimals Additional Example 2 B: Multiplying a Decimal by a Decimal 0. 07 0. 8 0. 07 1 = 0. 07 Estimate the product. 0. 8 is close to 1. 0. 07 0. 8 0. 056 Multiply. Then place the decimal point. 2 decimal places + 1 decimal place 3 decimal places; use a placeholder zero 0. 056 is close to the estimate of 0. 07. The answer is reasonable.

Multiplying Decimals Additional Example 2 C: Multiplying a Decimal by a Decimal 1. 34 2. 5 1 3=3 1. 34 2. 5 670 2680 3. 350 Estimate the product. Round each factor to the nearest whole number. Multiply. Then place the decimal point. 2 decimal places + 1 decimal place 3 decimal places 3. 350 is close to the estimate of 3. The answer is reasonable.

Multiplying Decimals Check It Out: Example 2 A Find the product. 0. 5 0. 2 Multiply. Then place the decimal point. 0. 5 1 decimal place 0. 2 + 1 decimal place 0. 10 2 decimal places

Multiplying Decimals Check It Out: Example 2 B 0. 03 0. 9 0. 03 1 = 0. 03 Estimate the product. 0. 9 is close to 1. 0. 03 0. 9 0. 027 Multiply. Then place the decimal point. 2 decimal places + 1 decimal place 3 decimal places; use a placeholder zero 0. 027 is close to the estimate of 0. 03. The answer is reasonable.

Multiplying Decimals Check It Out: Example 2 C 3. 80 3. 3 4 3 = 12 3. 80 3. 3 11400 12. 540 Estimate the product. Round each factor to the nearest whole number. Multiply. Then place the decimal point. 2 decimal places + 1 decimal places 3 decimal places 12. 54 is close to the estimate of 12. The answer is reasonable.

Multiplying Decimals Additional Example 3 A: Evaluating Decimal Expressions Evaluate 5 x for the value of x. x = 3. 062 5 x = 5(3. 062) Substitute 3. 062 for x. 3. 062 3 decimal places 5 + 0 decimal places 15. 310 3 decimal places Remember! These notations all mean multiply 3 times x. 3 • x 3 x 3(x)

Multiplying Decimals Additional Example 3 B: Evaluating Decimal Expressions Evaluate 5 x for the value of x. x = 4. 79 5 x = 5(4. 79) Substitute 4. 79 for x. 4. 79 2 decimal places 5 + 0 decimal places 23. 95 2 decimal places

Multiplying Decimals Check It Out: Example 3 A Evaluate 5 x for the value of x. x = 2. 012 5 x = 5(2. 012) Substitute 2. 012 for x. 2. 012 3 decimal places 5 + 0 decimal places 10. 060 3 decimal places

Multiplying Decimals Check It Out: Example 3 B Evaluate 5 x for the value of x. x = 6. 22 5 x = 5(6. 22) Substitute 6. 22 for x. 6. 22 2 decimal places 5 + 0 decimal places 31. 10 2 decimal places

Multiplying Decimals Lesson Quizzes Standard Lesson Quiz for Student Response Systems

Multiplying Decimals Lesson Quiz Find each product. 1. 0. 8 0. 07 0. 056 2. 0. 006 0. 07 0. 00042 Evaluate 8 x for each value of x. 3. x = 2. 705 21. 64 4. x = 0. 804 6. 432 5. “Pick your own” peaches sell for $0. 95 per pound. You picked 92 pounds of peaches. How much were you charged? $87. 40

Multiplying Decimals Lesson Quiz for Student Response Systems 1. Identify the product. 0. 29 0. 01 A. 0. 29 B. 0. 029 C. 0. 0029 D. 0. 00029

Multiplying Decimals Lesson Quiz for Student Response Systems 2. Identify the product. 0. 052 0. 03 A. 1. 0056 B. 0. 1056 C. 0. 0156 D. 0. 00156

Multiplying Decimals Lesson Quiz for Student Response Systems 3. Evaluate 4 x for x = 5. 325. A. 21 B. 21. 2 C. 21. 28 D. 21. 3

Multiplying Decimals Lesson Quiz for Student Response Systems 4. Evaluate 9 x for x = 0. 012. A. 10. 8 B. 1. 08 C. 0. 108 D. 0. 0108

Multiplying Decimals Lesson Quiz for Student Response Systems 5. Strawberry lemonade costs $0. 89 per packet. Karen bought 58 packets of strawberry lemonade for a picnic. How much did she pay for it? A. $51. 62 B. $51. 86 C. $52. 54 D. $52. 93