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Decimals Review by Lauren McCluskey Decimal Models Tenth Hundredth by Christine Berg Remember that each period has three place values within the period 671,690,492.36754 by Moncia Yuskaitis Equivalent Decimals 0.6 or 6 tenths 0.60 or 60 hundredths by Christine Berg Use rounding • When the question asks you to estimate. • When you want to know if your answer is reasonable. by Monica Yuskaitis Memorize this Poem Find your number. Look right next door. 4 or less just ignore. 5 or more, add 1 more. by Monica Yuskaitis Round to the tenths: 75.86 75.83 75.96 75.835 Find your number. Look right next door. 4 or less just ignore. 5 or more, add 1 more. 75.86 is about 75.9 75.83 is about 75.8 75.96 is about 76.0 75.835 is about 75.8 Which is greater: 0.6 or 0.58? 0.6 0.58 by Christine Berg Which is greater: 0.400 or 0.5? 0.400 0.5 by Christine Berg Adding or Subtracting Decimals When adding or subtracting decimals, line them up! What is: 1. $7.54 + $3.56? 2. $15.00 - $6.27? 3. $0.75 + $1.25 + $6.79? 4. 75.425 + 3.5005? 5. 98.322 – 7.0545? Adding or Subtracting Decimals When adding or subtracting decimals, line them up! What is: 1. $7.54 + $3.56 = $11.10 2. $15.00 - $6.27 = $8.73 3. $0.75 + $1.25 + $6.79 = $8.79 4. 75.425 + 3.5005 =78.9255 5. 98.322 – 7.0545 = 91.2675 Multiplying Decimals Multiplying decimals is counterintuitive. What is 0.10 * 6? Think about money. 0.10 is a dime, and you have 6 of them, so how much do you have? 0.60. Multiplying Decimals 0.1 * 0.6 = Multiplying Decimals 0.06 0.1 * 0.6 = Or… one tenth of 6 tenths is 6 hundredths. Try it! 1. 2. 3. 2.50 * 0.1 ? 87.655 * 0.001? 125.75 * 1.0? Try it! 1. 2. 3. 2.50 * 0.1 = 0.250 87.655 * 0.001 = 0.087655 125.75 * 1.0 = 12.575 Dividing Decimals Dividing decimals can be counter-intuitive. Dividing a decimal by a decimal can give you a larger number. 0.6 ÷ 0.1= Or… there are 6 tenths in 0.6. 6 tenths Try it! 1. 2. 3. 875.25 ÷ 0.01 ? 9218.4 ÷ 0.1? 722.36 ÷ 0.0001? Try it! 1. 2. 3. 875.25 ÷ 0.01 = 87,525 9218.4 ÷ 0.1 = 92,184 722.36 ÷ 0.0001 = 7,223,600 Credits: Comparing and Rounding Decimals by Christine Berg Math Flash Place Value by Monica Yuskaitis Math Flash Rounding by Monica Yuskaitis