Estimating Sums and Differences. Amanda Hobson. Objectives:. The students will: 1. Give the definition of Estimation. 2. Explain the differences in rounding and front-end estimation. 3. Estimate the sums or differences using the two methods. Estimation.
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Estimating Sums and Differences
The students will:
1. Give the definition of Estimation.
2. Explain the differences in rounding and front-end estimation.
3. Estimate the sums or differences using the two methods.
Finding the value that is close enough to the right answer, usually with some thought or calculation.
Rounding means reducing the digits in a number while trying to keep its value similar. The result is less accurate, but easier to use.
73 rounded to the nearest ten is 70 because the 3 is less than 5; therefore the number 73 will be rounded down.
Example: (round to the nearest ten) 26 + 14
+ 14 + 10
Example: (round to the nearest thousand) 5,976 - 2,687
-2,687 - 3,000
A method in which the front digits in the given numbers are added or subtracted
Front end estimation mostly produces a closer estimate of sums or differences than the answer produced by adding or subtracting rounded numbers.
Example: 44,859 + 25,789
+ 25,789 + 20,000
Example: 57,658 - 24,125
- 24,125 - 20,000
Subtract the values of the front digits.
1,431 - 1,000
Round to the nearest ten thousand.
Add the values of the front digits.
+ 2,415 + 2,000
Round to the nearest thousand.
+ 1,452 + 1,000