 # 3-5 Multiplying Decimals Warm Up Problem of the Day

## Presentation on theme: "3-5 Multiplying Decimals Warm Up Problem of the Day"— Presentation transcript:

3-5 Multiplying Decimals Warm Up Problem of the Day
Course 1 Warm Up Problem of the Day Lesson Presentation

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

3-5 Multiplying Decimals Problem of the Day
Course 1 3-5 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

3-5 Multiplying Decimals
Course 1 3-5 Multiplying Decimals Learn to multiply decimals by whole numbers and by decimals.

Course 1 3-5 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. 4  0.17 17 Multiply as you would with whole numbers.  4 68

Course 1 3-5 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 2 decimal places  4 + 0 decimal places 0.68 2 decimal places A 4 lb dumbbell on Earth weighs 0.68 lb on the Moon.

3-5 Multiplying Decimals  7 Check It Out: Example 1
Course 1 3-5 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? Multiply 7 by 0.17, since 1 pound on Earth is 0.17 pound on the Moon. 7  0.17 17 Multiply as you would with whole numbers.  7 119

Check It Out: Example 1 Continued
Course 1 3-5 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 2 decimal places  7 + 0 decimal places 1.19 2 decimal places A 7 lb dumbbell on Earth weighs 1.19 lb on the Moon.

Course 1 3-5 Multiplying Decimals You can use a decimal grid to model multiplication of decimals. Helpful Hint

Additional Example 2A: Multiplying a Decimal by a Decimal
Course 1 3-5 Multiplying Decimals Additional Example 2A: Multiplying a Decimal by a Decimal Find the product. 0.3  0.4 Multiply. Then place the decimal point. 1 decimal place 0.3 + 1 decimal place 0.4 2 decimal places 0.12

Additional Example 2B: Multiplying a Decimal by a Decimal
Course 1 3-5 Multiplying Decimals Additional Example 2B: Multiplying a Decimal by a Decimal 0.07  0.8 Estimate the product. 0.8 is close to 1. 0.07  1 = 0.07 Multiply. Then place the decimal point. 2 decimal places 0.07  0.8 + 1 decimal place 3 decimal places; use a placeholder zero 0.056 0.056 is close to the estimate of The answer is reasonable.

Additional Example 2C: Multiplying a Decimal by a Decimal
Course 1 3-5 Multiplying Decimals Additional Example 2C: Multiplying a Decimal by a Decimal 1.34  2.5 Estimate the product. Round each factor to the nearest whole number. 1  3 = 3 Multiply. Then place the decimal point. 1.34 2.5 2 decimal places 670 + 1 decimal place 2680 3 decimal places 3.350 3.350 is close to the estimate of 3. The answer is reasonable.

3-5 Multiplying Decimals  Check It Out: Example 2A Find the product.
Course 1 3-5 Multiplying Decimals Check It Out: Example 2A Find the product. 0.5  0.2 Multiply. Then place the decimal point. 1 decimal place 0.5 + 1 decimal place 0.2 2 decimal places 0.10

3-5 Multiplying Decimals  Check It Out: Example 2B 0.03  0.9
Course 1 3-5 Multiplying Decimals Check It Out: Example 2B 0.03  0.9 Estimate the product. 0.9 is close to 1. 0.03  1 = 0.03 Multiply. Then place the decimal point. 0.03 2 decimal places 0.9 + 1 decimal place 0.027 3 decimal places; use a placeholder zero 0.027 is close to the estimate of The answer is reasonable.

3-5 Multiplying Decimals  Check It Out: Example 2C 3.80  3.3
Course 1 3-5 Multiplying Decimals Check It Out: Example 2C 3.80  3.3 Estimate the product. Round each factor to the nearest whole number. 4  3 = 12 Multiply. Then place the decimal point. 3.80 3.3 2 decimal places 1140 + 1 decimal places 11400 3 decimal places 12.540 12.54 is close to the estimate of 12. The answer is reasonable.

Additional Example 3A: Evaluating Decimal Expressions
Course 1 3-5 Multiplying Decimals Additional Example 3A: Evaluating Decimal Expressions Evaluate 5x for the value of x. x = 3.062 Substitute for x. 5x = 5(3.062) 3 decimal places 3.062 5 + 0 decimal places 15.310 3 decimal places These notations all mean multiply 3 times x. 3 • x 3x 3(x) Remember!

Additional Example 3B: Evaluating Decimal Expressions
Course 1 3-5 Multiplying Decimals Additional Example 3B: Evaluating Decimal Expressions Evaluate 5x for the value of x. x = 4.79 Substitute 4.79 for x. 5x = 5(4.79) 2 decimal places 4.79 5 + 0 decimal places 23.95 2 decimal places

3-5 Multiplying Decimals  Check It Out: Example 3A
Course 1 3-5 Multiplying Decimals Check It Out: Example 3A Evaluate 5x for the value of x. x = 2.012 Substitute for x. 5x = 5(2.012) 3 decimal places 2.012 5 + 0 decimal places 10.060 3 decimal places

3-5 Multiplying Decimals  Check It Out: Example 3B
Course 1 3-5 Multiplying Decimals Check It Out: Example 3B Evaluate 5x for the value of x. x = 6.22 Substitute 6.22 for x. 5x = 5(6.22) 2 decimal places 6.22 5 + 0 decimal places 31.10 2 decimal places

Insert Lesson Title Here
Course 1 3-5 Multiplying Decimals Insert Lesson Title Here Lesson Quiz Find each product.  0.07 Evaluate 8x for each value of x.  0.07 0.056 3. x = x = 0.804 21.64 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