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4.4

Multiplying Decimals and Circumference of a Circle. 4.4. Multiplying Decimals. Multiplying decimals is similar to whole numbers. The only difference is that we place a decimal point in the product. Multiplying Decimals Step 1: Multiply the decimals as though they are whole numbers.

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4.4

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  1. Multiplying Decimals and Circumference of a Circle 4.4

  2. Multiplying Decimals Multiplying decimals is similar to whole numbers. The only difference is that we place a decimal point in the product. Multiplying Decimals Step 1: Multiply the decimals as though they are whole numbers. Step 2: The decimal point in the product is placed so that the number of decimal places in the product is equal to the sum of the number of decimal place in the factors.

  3. Multiplying Decimals Total of 2 decimal places. Decimal placed at two decimal places.

  4. Example Multiply: 15.9 × 0.62 1 decimal place 2 decimal places Insert the decimal point in the product so that there are 3 decimal places (1 + 2 = 3).

  5. Example Multiply: 0.648 × 0.5 3 decimal places 1 decimal place Insert the decimal point in the product so that there are 4 decimal places.

  6. Multiplying Decimals Practice Problems 1 decimal place 3 decimal places 2 decimal places 1 decimal place 1+2=3 decimal places 3+1=4 decimal places P 275

  7. Multiplying Decimals Practice Problems 4 decimal place 0 decimal places 4+0=4 decimal places P 276

  8. Estimating when Multiplying Decimals We can estimate when multiplying decimals to check for reasonableness. Example: Exact Estimate Since 22.26 is close to our estimate of 20, it is a reasonable answer.

  9. Estimating When Multiplying Decimals Practice Problem 4 Multiply: SOLUTION Round to the ones Exact Estimate Since 90.1748 is close to our estimate of 90, it is a reasonable answer. P 276

  10. Multiplying by Powers of 10

  11. Example Multiply. 58.1 × 0.01 85,624 × 0.1 24.106 ×100 = 0.581 Move the decimal point 2 places to the left = 8562.4 Move the decimal point 1 place to the left. = 2410.6 Move the decimal point 2 places to the right.

  12. Multiplying by Powers of 10 Practice Problems P 277

  13. Multiplying by Powers of 10 Practice Problems P 277

  14. Finding the Circumference of a Circle radius diameter The two common approximations for

  15. 9.1 yards Example Find the circumference of the following circle. Circumference =

  16. Solving Problems by Multiplying Decimals Jose Severos, an electrician for Central Power and Light, worked 40 hours last week. Calculate his pay before taxes for last week if his hourly wage is $13.88. Jose Severos’ pay before taxes for last week is $555.20.

  17. Finding the Circumference of a Circle Practice Problem 12 Find the circumference of a circle whose radius is 11 meters. Then use the approximations 3.14 for π to approximate this circumference. 11 meters SOLUTION P 278

  18. DONE

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