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3-4: Estimating Sums and Differences

3-4: Estimating Sums and Differences. Rounding Clustering Front-end-estimating . Rounding. Most of the time, you will be asked to round to the nearest whole number. Round to the ones place, and drop the decimal part of your number. Example: Estimate the sum of 10.93 and 3.25. 11.

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3-4: Estimating Sums and Differences

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  1. 3-4: Estimating Sums and Differences Rounding Clustering Front-end-estimating

  2. Rounding • Most of the time, you will be asked to round to the nearest whole number. • Round to the ones place, and drop the decimal part of your number.

  3. Example: Estimate the sum of 10.93 and 3.25. 11 11.00 10.93 3.00 3 3.25 + 14

  4. Clustering • Use when all numbers are close to the same amount • If so, round each number to the same number. • Then multiply • Ex) $2.44 + $1.86 + $2.11 + $1.70 $2 x 4 = $8

  5. Front End Estimation • Add or subtract the values of the digits in the front place or left-most place value. • Usually gives a sum that is less than the actual sum.

  6. Example 5.45 9.89 3.53 6.03 Front-end: 5 + 9 + 3 + 6 = 23 + About 23

  7. Try P152 # 1-9 • 0+1 = 1 • $15 + $32 = $47 • 4 – 3 = 1 • 60 – 20 = 40 • 3 x 5 = 15 • $3 x $1 = $3 • C • 100 + 500 = 600 • $400 - $100 = $300 The above image is a royalty free picture provided by http://www.bigfoto.com

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