Is It Reasonable?

Round to estimate, then check an answer against the estimate.

Warm-up, learn, try it together, practice, then a quick check. About 15 minutes.

What children learn in Level 17

An estimate helps you check whether an answer makes sense. Estimate 38,452 plus 21,317 by rounding to the nearest ten thousand.
38,452 rounds to 40,000, and 21,317 rounds to 20,000. 40,000 plus 20,000 is 60,000, so the answer should be close to 60,000.
If someone says the answer is 95,769, that's far from 60,000. Not reasonable! The real answer, 59,769, is close. Reasonable!
Rounding to the nearest thousand gives a closer estimate: 38,000 plus 21,000 is 59,000.

Georgia's K-12 Mathematics Standards:

4.NR.2.5 — Solve multi-step problems using addition, subtraction, multiplication, and division involving whole numbers. Use mental computation and estimation strategies to justify the reasonableness of solutions.
4.NR.1.4 — Use place value understanding to round multi-digit whole numbers.