Estimation of a difference involves replacing two-digit or accessible three-digit whole numbers up to 1,000 with nearby friendly tens or hundreds, then determining the approximate amount left by subtraction. Place value and number-line reasoning help judge whether the result should be close to zero, tens, or hundreds and check whether an exact difference is reasonable; formal error bounds, decimals, fractions, and estimation with larger numbers are beyond this understanding.
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Detailed Explanation: Estimate differences informally
To estimate a difference, replace each number with a nearby friendly ten or hundred. Then subtract the friendly numbers.
Example: Estimate .
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Find a nearby ten for each number:
- is close to .
- is close to .
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Subtract the friendly numbers:
- So, the estimated difference is about .
This makes sense because and are both close to and , and the amount left should be a few tens, not hundreds.
Learn by doing: Estimate differences informally
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Practice:
Subtraction - Estimate Difference - 2 & 2 Digit
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Download/Modify Free Grade 2 'Estimate differences informally' Worksheet
Print this free 'Estimate differences informally' worksheet to practice this skill away from the computer. Click 'Modify' to easily customize this worksheet to your exact needs.
This Worksheet Includes:
- Subtraction - Estimate Difference - 2 & 2 Digit
- Subtraction - Estimate Difference - 3 & 3 Digit
- Subtraction - Estimate Difference - 3 & 2 Digit
- Subtraction - Whole Number 2 x 2, No Borrow
- Subtraction - Whole Number 3 x 2, No Borrow
- Addition - Estimate Sum - 2 & 2 Digit
- Compare Two-Digit Numbers to 100
- Compare Two- or Three-Digit Numbers to 500
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