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Chapter 1 Multiply & Divide Decimals

Chapter 1 Multiply & Divide Decimals. 1-1 A : Estimate Products. To Estimate Decimals round to the nearest whole number as follows: *** Underline the digit to be rounded. If the digit to the RIGHT of the place being rounded is: 4 or less, keep the underlined digit the same

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Chapter 1 Multiply & Divide Decimals

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  1. Chapter 1 Multiply & Divide Decimals

  2. 1-1 A: Estimate Products • To Estimate Decimals round to the nearest whole number as follows: ***Underline the digit to be rounded. If the digit to the RIGHT of the place being rounded is: • 4 or less, keep the underlined digit the same • 5 or greater, round the underlined digit up by 1 Ex: 15.6 » 16 or 15.3 » 15

  3. 1-1 C: Multiply Decimals by Whole Numbers • Multiply the Whole Number & the Decimal Number ex: 1.42 x 3 4 26 • Count the # of digits to the RIGHT of the decimal point • Place the decimal point the same # of places FROM the right in your answer. 2 decimal places . 2 decimal places

  4. 1-1(D & E) Multiply Decimals by Decimals Multiply as you would with whole numbers, then place the decimal point. The # of places in the answer = the # of decimal places in both factors. 3.14(2 decimal places) x15.6(1 decimal place) 1884 15700 + 31400 48.984(3 decimal places)

  5. 1-2 A: Estimate Quotients To estimate quotients of decimals, use Rounding and Compatiblenumbers. • Rounding: 8.75÷ 3 » 9 ÷ 3 = 3 • Compatible numbers: (#s that are easy to divide). 30.8 ÷ 3.9 use 32 ÷ 4because 32 & 4 are compatible numbers & divide evenly.

  6. 1-2 B: Dividing Decimals by a Whole number • Divide as with whole numbers & then place the decimal point in the quotient (answer) directly above its place in the dividend. 6.8 ÷ 2 » 2)6.8 -6 0 8 - 8 0 . 3 4

  7. 1-2 E: Divide Decimals by Decimals • When dividing by a decimal, change the divisor into a whole number by moving the decimal point all the way to the RIGHT. • Move the decimal point in the dividend the same number of spaces, then divide. 6.84 ÷ 0.02 » 2 )684 -6 08 - 8 04 - 4 0 . . . . 3 4 2 = 342 or 342 .

  8. 1-3 A: Multiply by Powers of 10 • Muliplying a decimal by a Power of 10 > than 1 moves the decimal point to the RIGHT the same number of places as zeros in the power of 10. Ex: .35 x 100 = Ex: 8.5 x 1000 = • Multiplying a decimal by a Power of 10 < 1 moves the decimal point to the LEFT the same number of places as there are after the decimal point. Ex: 5.4 x 0.01 = Ex: 12.4 x 0.001 = 35 8500 0.0124 0.054

  9. Divide by Powers of 10 • Dividing by a Power of 10 > 1 moves the decimal point to the LEFT the # of places as the number of zeros in the power of 10. • Ex: 81.7 ÷ 100 = • Dividing a decimal by a Power of 10 < 1 moves the decimal point to the RIGHT the same # of places as there are after the decimal point. • Ex: 4.57 ÷ 0.1 = .817 45.7

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