Decimals Review

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Decimals Review

• by Lauren McCluskey

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Decimal Models
Tenth
Hundredth
by Christine Berg
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Remember that each period hasthree place values
within the period
Ten -thousandths Hundred-thousandths
Tenths Hundredths Thousandths
Hundreds Tens Million Ones
Hundreds Tens Thousand Ones
Hundreds Tens Ones Ones
671,690,492.36754
by Moncia Yuskaitis
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Equivalent Decimals
0.6 or 6 tenths
0.60 or 60 hundredths
by Christine Berg
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Use rounding

• When the question asks you
• to estimate.
• When you want to know if your answer is
  reasonable.

by Monica Yuskaitis
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Memorize this Poem
Find your number. Look right next door. 4 or less
just ignore. 5 or more, add 1 more.
by Monica Yuskaitis
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Round to the tenths

• 75.86
• 75.83
• 75.96
• 75.835

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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

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Which is greater 0.6 or 0.58?
0.6
0.58
by Christine Berg
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Which is greater 0.400 or 0.5?
0.400
0.5
by Christine Berg
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Adding or Subtracting Decimals

• When adding or subtracting decimals, line them
  up!
• What is
• 7.54 3.56?
• 15.00 - 6.27?
• 0.75 1.25 6.79?
• 75.425 3.5005?
• 98.322 7.0545?

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Adding or Subtracting Decimals

• When adding or subtracting decimals, line them
  up!
• What is
• 7.54 3.56 11.10
• 15.00 - 6.27 8.73
• 0.75 1.25 6.79 8.79
• 75.425 3.5005 78.9255
• 98.322 7.0545 91.2675

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Multiplying Decimals

• Multiplying decimals is counter-intuitive.
• 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.

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Multiplying Decimals

0.6
0.1
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Multiplying Decimals
0.06


0.6
0.1
Or one tenth of 6 tenths is 6 hundredths.
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Try it!

1. 2.50 0.1 ?
2. 87.655 0.001?
3. 125.75 1.0?

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Try it!

• 2.50 0.1 0.250
• 87.655 0.001 0.087655
• 125.75 1.0 12.575

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Dividing Decimals
Dividing decimals can be counter-intuitive.
Dividing a decimal by a decimal can give you a
larger number.

6 tenths
0.6
0.1







Or there are 6 tenths in 0.6.
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Try it!

• 875.25 0.01 ?
• 9218.4 0.1?
• 722.36 0.0001?

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Try it!

• 875.25 0.01 87,525
• 9218.4 0.1 92,184
• 722.36 0.0001 7,223,600

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Credits

• Comparing and Rounding Decimals by Christine Berg
• Math Flash Place Value by Monica Yuskaitis
• Math Flash Rounding by Monica Yuskaitis