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5 Minute Check Complete in your notebook. Estimate each product. 1. 9.7 x 3 2. 3.4 x 5 3. 17.5 x 8 Multiply. 4. 1.5 x 6 5. 3.1 x 13 6. 3.48 x 25 5 Minute Check Complete in your notebook. Estimate each product. 1. 9.7 x 3 5 Minute Check Complete in your notebook. Estimate each product. 1. 9.7 x 3 10 x 3 = 30 5 Minute Check Complete in your notebook. Estimate each product. 2. 3.4 x 5 5 Minute Check Complete in your notebook. Estimate each product. 2. 3.4 x 5 3 x 5 = 15 5 Minute Check Complete in your notebook. Estimate each product. 3. 17.5 x 8 5 Minute Check Complete in your notebook. Estimate each product. 3. 17.5 x 8 18 x 8 = 144 5 Minute Check Complete in your notebook. Multiply. 4. 1.5 x 6 5 Minute Check Complete in your notebook. Multiply. 4. 1.5 x 6 1.5 x 6 9.0 1 decimal place 1 decimal place 5 Minute Check Complete in your notebook. Multiply. 5. 3.1 x 13 5 Minute Check Complete in your notebook. Multiply. 5. 3.1 x 13 3.1 x 13 93 + 310 40.3 1 decimal place 1 decimal place Don’t forget the zero 5 Minute Check Complete in your notebook. Multiply. 6. 3.48 x 25 5 Minute Check Complete in your notebook. Multiply. 6. 3.48 x 25 3.48 2 decimal places x 25 1740 + 6960 87.00 2 decimal places Don’t forget the zero Flashcards! Wednesday, Oct 9 Lesson 3.2 and 3.4 Multiplying Decimals by Decimals Multiplying Decimals by Decimals Objective: To understand how to estimate and multiply decimals by decimals. Multiplying Decimals by Decimals At the end of this lesson you should be able to answer the following questions. How do you determine which place value to use when multiplying decimals by decimals? Why is estimating not as helpful when multiplying very small numbers? Multiplying Decimals by Decimals To multiply decimals, multiply as normal and then place the decimal point. Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. First round the numbers to the nearest whole number to get an estimate. What does 8.7 round to? Digits from 0 to 4 round down and digits from 5-9 round up. Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. First round the numbers to the nearest whole number to get an estimate. What does 8.7 round to? 9 What does 2.8 round to? Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. First round the numbers to the nearest whole number to get an estimate. What does 8.7 round to? 9 What does 2.8 round to? 3 Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. First round the numbers to the nearest whole number to get an estimate. 9 x 3 = 27, so 8.7 x 2.8 ≈ 27 Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. To multiply decimals. Step 1 – Stack the numbers with the number with the most digits on top. 8.7 x 2.8 (Since both numbers have 2 digits, either could be on top) Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. To multiply decimals. Step 2 – Multiply the digits. 8.7 x 2.8 696 +1740 2436 Don’t forget to add the zero. Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. To multiply decimals. Step 3 – Determine the number of decimal places in the factors to locate the decimal place in the product. 8.7 1 decimal place x 2.8 + 1 decimal place 696 +1740 24.36 2 decimal places Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. 8.7 x 2.8 696 +1740 24.36 Is this a reasonable answer? Multiplying Decimals by Decimals Find the product of 8.7 and 2.8. Is this a reasonable answer? 24.35 ≈ 27 Multiplying Decimals by Decimals Find the product of .98 and 7.3 Estimate? Multiplying Decimals by Decimals Find the product of .98 and 7.3 Estimate? 1 x 7 = 7, so .98 x 7.3 ≈ 7 Next? Multiplying Decimals by Decimals Find the product of .98 and 7.3 .98 x 7.3 Next? Multiplying Decimals by Decimals Find the product of .98 and 7.3 .98 x 7.3 294 +6860 7154 Next? Don’t forget to add a zero Multiplying Decimals by Decimals Find the product of .98 and 7.3 .98 x 7.3 294 +6860 7.154 2 decimal places +1 decimal place 3 decimal places Is this a reasonable answer? Multiplying Decimals by Decimals Find the product of .98 and 7.3 .98 x 7.3 294 +6860 7.154 2 decimal places +1 decimal place 3 decimal places Is this a reasonable answer? 7.154 ≈ 7 Multiplying Decimals by Decimals Find the product of 3.6 and 0.05. Estimate? Multiplying Decimals by Decimals Find the product of 3.6 and 0.05. 4 x 0 = 0, so 3.6 x 0.05 ≈ 0 Multiplying Decimals by Decimals Find the product of 3.6 and 0.05. 4 x 0 = 4, so 3.6 x 0.05 ≈ 0 Actual product? Multiplying Decimals by Decimals Find the product of 3.6 and 0.05 0.05 x 3.6 0030 + 0015 0.045 2 decimal places +1 decimal place 3 decimal places Is this a reasonable answer? Multiplying Decimals by Decimals Find the product of 3.6 and 0.05 0.05 x 3.6 030 +0150 0.180 2 decimal places +1 decimal place 3 decimal places Is this a reasonable answer? 0.180 ≈ 0 Multiplying Decimals by Decimals Find the product of 0.112 and 7.2 Estimate? Multiplying Decimals by Decimals Find the product of 0.112 and 7.2 Estimate? 0 x 7 = 0, so 0.112 x 7.2 ≈ 0 Actual product? Multiplying Decimals by Decimals Find the product of 0.112 and 7.2 0.112 x 7.2 0224 +07840 .8064 3 decimal places +1 decimal place 4 decimal places Is this a reasonable answer? Multiplying Decimals by Decimals Find the product of 0.112 and 7.2 0.112 x 7.2 0224 +07840 .8064 3 decimal places +1 decimal place 4 decimal places Is this a reasonable answer? 0.8064 ≈ 0 Multiplying Decimals by Decimals Find the product of 1.4 and 0.067 Estimate? Multiplying Decimals by Decimals Find the product of 1.4 and 0.067 Estimate? 1x0=0 1.4 x 0.067 ≈ 0 Actual product? Multiplying Decimals by Decimals Find the product of 1.4 and 0.067 0.067 x 1.4 0268 +00670 0.0938 3 decimal places +1 decimal place 4 decimal places Is this a reasonable answer? Multiplying Decimals by Decimals Find the product of 1.4 and 0.067 0.067 x 1.4 0268 +00670 0.0938 3 decimal places +1 decimal place 4 decimal places Is this a reasonable answer? 0.0938 ≈ 0 Multiplying Decimals by Decimals Mr. Avery’s car can travel 28.45 miles on one gallon of gas. If his gas tank holds 11.5 gallons, how far can he travel on one tank? Estimate? Multiplying Decimals by Decimals Mr. Avery’s car can travel 28.45 miles on one gallon of gas. If his gas tank holds 11.5 gallons, how far can he travel on one tank? Estimate? 28 x 12 = 336 Keep in mind 28 x 12 = 28 x 10 + 28 x 2 = 280 + 56 = 336 Actual product? Multiplying Decimals by Decimals Mr. Avery’s car can travel 28.45 miles on one gallon of gas. If his gas tank holds 11.5 gallons, how far can he travel on one tank? 28.45 x 11.5 14225 28450 +284500 327.175 2 decimal places +1 decimal place 3 decimal places Is this a reasonable answer? Multiplying Decimals by Decimals Mr. Avery’s car can travel 28.45 miles on one gallon of gas. If his gas tank holds 11.5 gallons, how far can he travel on one tank? 28.45 x 11.5 14225 28450 +284500 327.175 2 decimal places +1 decimal place 3 decimal places Is this a reasonable answer? 327.175 ≈ 336 Multiplying Decimals by Decimals Determine whether the following statement is always, sometimes or never true. The product of two decimals less than 1 is less than either of the factors. Give examples to support your answer. Multiplying Decimals by Decimals Determine whether the following statement is always, sometimes or never true. The product of two decimals less than 1 is less than either of the factors. Always. 0.3 x 0.5 = .15, which is less than 0.3 and 0.5 0.75 x 0.6 = 0.45 Multiplying Decimals by Decimals Complete the Mid-Chapter Check on page 214. When complete bring to the desk and show Mr. Avery. Agenda Notes Homework –Homework Practice 3-2/3-4 Due Thursday, Oct 10 Mid-Chapter 3 Quiz –Thursday, Oct 10