Estimating a difference involves replacing whole-number minuends and subtrahends with nearby, compatible values—often by rounding to a common place value—and subtracting to obtain a reasonable approximation. The estimate should reflect place-value relationships, account for how rounding each number affects the result, and be checked for plausibility using an open number line or the exact computation; the focus is whole-number quantities, not decimal or integer differences.
Detailed Explanation: Estimate differences of whole numbers
To estimate a difference, replace both numbers with nearby numbers that are easier to subtract. Round both numbers to the same place value, then subtract.
Example: Estimate 84,732−29,468.
Choose a place value.
Round both numbers to the nearest thousand.
Round each number.
84,732 rounds to 85,000 because the hundreds digit is 7.
29,468 rounds to 29,000 because the hundreds digit is 4.
Subtract the rounded numbers.
85,000−29,000=56,000
So,
84,732−29,468≈56,000.
Check that the estimate is reasonable.
The exact difference is 55,264, which is close to 56,000. Also, rounding changed the first number up and the second number down, so the estimated difference should be a little larger than the exact difference. That makes 56,000 plausible.
Learn by doing: Estimate differences of whole numbers
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