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4.4 Estimating with Decimals

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Homework

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Mental Math Give a whole-number estimate for these decimal addition problems. Show which whole numbers you used: 3.8 + 9.9 = EXAMPLE: 4 + 10 = 14 2.7 + 8.1 = 10.5 – 6.6 = 8.8 + 8.9 = 23.7 – 8.8 = 25.5 + 11.9 = 26.2 – 10.8 =

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Math Message Turn to a tablemate and describe two examples in which decimals are used in real-life situations. Measurement: Money: Other:

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Why are decimals useful? SRB Page 26:

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Trip Meters and Speedometers What information would we get if it just showed whole numbers of miles traveled? Decimals make it possible to have a more precise measurement of distance traveled. Below the speedometer shows tenths of a mile. Have you traveled closer to 45 miles or 46?

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How do I round decimals? Rounding decimals are very similar to rounding whole numbers-the only difference is there is a decimal point! Look at the digit to the right of the place you are rounding Think about this poem If it is 4 or less just ignore, If it is 5 or more add one more!

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Rounding to the nearest tenth Round to the nearest tenth 5.263 –The number to the right of the 2 is a six. – Six is greater than five, so I need to add one more the 2. The 2 becomes a 3 and everything after becomes a 0 – 5.263 rounded to the nearest tenth become 5.300 or 5.3

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Rounding to the Nearest Hundredth Round to the nearest hundredth Remember 4 or less just ignore, 5 or more add one more! 3.653 The number to the right of the 5 is an 3. 3 is less than 4, so we just ignore- meaning the five in the hundredths place stays the same. The 5 stays the same and all the other numbers after it become zeros The correct answer is: 3.650 or 3.65

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More Practice 2.34 46.675 232.23 96.782 0.45 12.322

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Estimating Decimal Sums MJ p 85 Must answer the questions by using ESTIMATION, not by calculating exact answers.

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Partnership Work – MJ p. 83

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MJ 85

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Wrapping it UP! In your math notebook, solve the following problems using estimation. 3.67 + 0.7 5.23 - 1.1 Write one new fact you learned about estimating decimals.

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Homework – Study Link 4.4

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Math Box 4.4

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