Check: Using Estimation to Assess Reasonableness
This Grade 4 Eureka Math skill teaches students to check the reasonableness of a multi-step answer by comparing it to an estimate made through rounding. Students round each number in the problem to a convenient place value, compute the estimate, and verify that the precise answer is close to it. For a library problem where 28,455 minus 5,981 plus 2,120 is calculated, rounding to the nearest thousand gives 28,000 minus 6,000 plus 2,000 = 24,000, and the precise answer of 24,594 is close, confirming reasonableness. This checking strategy is from Chapter 5 of Eureka Math Grade 4.
Key Concepts
To assess the reasonableness of a precise answer, compare it to an estimate made by rounding the numbers in the problem. If the precise answer is close to the estimated answer, it is likely reasonable. This can be represented as: $$Answer {precise} \approx Answer {estimate}$$.
Common Questions
What does it mean to check the reasonableness of an answer?
Comparing your exact answer to a rough estimate to verify they are close. If they differ significantly, the exact calculation likely has an error.
How do you estimate to check reasonableness?
Round each number in the problem to a convenient place value (usually the leading digit), perform the operation on the rounded numbers, and compare to your precise answer.
How do you check the answer for 28,455 minus 5,981 plus 2,120?
Round: 28,000 minus 6,000 + 2,000 = 24,000. Precise answer: 24,594. Since 24,594 is close to 24,000, the answer is reasonable.
What does the approximately equal symbol mean?
The symbol means approximately equal to. It indicates the estimate is not exact but close enough to confirm reasonableness.
When is an answer unreasonable?
If the precise answer differs greatly from the estimate (for example, being thousands away with no justification), the calculation likely contains an error such as a misaligned digit or a sign mistake.