Using Estimation to Check Reasonableness
Using Estimation to Check Reasonableness is a Grade 3 math skill from Eureka Math teaching students to verify calculated answers by comparing them to estimates. The process: round the problem's numbers to easy values, perform the same steps with the rounded numbers, then check that the exact answer and the estimated answer are close. If the answers differ greatly, a calculation error likely occurred. This habit of estimating before or after solving builds number sense and reduces errors in multi-step arithmetic.
Key Concepts
To assess reasonableness, round the numbers in the problem to nearby, easy to work with values. Then, perform the same two steps of the problem using these rounded numbers. The result of your estimation should be close to your calculated answer.
Common Questions
How do you use estimation to check if an answer is reasonable?
Round the numbers in the problem to nearby easy values. Perform the same calculation steps with the rounded numbers. Compare your estimated result to the exact answer—they should be close.
What does 'reasonable' mean in math?
A reasonable answer is one that makes sense given the size of the numbers in the problem. An answer that is far from the estimate is likely the result of a calculation error.
What rounding values are used when estimating in Grade 3?
Third graders typically round to the nearest 10 or 100, choosing values that make mental arithmetic easy while staying close to the original numbers.
Why should the estimated answer and the exact answer be close?
Rounding changes numbers slightly but not drastically. The estimate is an approximation of the real calculation, so a correct exact answer and a good estimate should be in the same range.
In which textbook is Using Estimation to Check Reasonableness taught?
This skill is taught in Eureka Math, Grade 3.