An informal estimate of a sum is a nearby, easier total found by using place-value structure, such as replacing two-digit addends with the nearest tens or choosing compatible numbers. The estimate should preserve the sum’s approximate size, allow a student to judge whether an exact answer is reasonable, and may be recognized as above or below the actual total; it is not the exact sum. More formal estimation with larger numbers, decimals, or general error bounds is not included.
An estimate is a nearby answer that is easier to find. It is not the exact sum.
To estimate a sum:
Example: Estimate .
So, the estimated sum is about .
The exact sum is , so is a reasonable estimate and is close to the actual answer.
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