Check Exact Multi-Digit Calculations with an Estimate

Supplied materials

• Paper and a pencil; drawing and spoken explanations are welcome. An adult may read directions and options aloud.
• Supplied worked-case record: Calculate 536−278.
• All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

Exact addition and subtraction depend on matching place values and recording exchanges accurately. An estimate helps catch an answer that is far too large or small. It does not prove every digit is correct, so also use an inverse calculation or a second model.

Compute the supplied exact operation with place value. Estimate by nearby hundreds to check scale, then verify the exact result with subtraction or addition. State which result is exact and which is approximate.

Use an inverse operation for an exact check. A plausible estimate does not prove every digit of an exact answer. Write a place-value calculation next to a separately labeled estimate.

1. Write a place-value calculation next to a separately labeled estimate.
2. Follow the worked example. Point to each number or shape feature and say what it tells you.
3. Compute the supplied exact operation with place value.
4. Try the question and then the three practice questions. Check your answers and explain any change you make.

Check your reasoning

Your answer is temporary and is not saved to an account. Download your current answer before leaving or reloading. Written work on paper or in another app stays in your own file.

Take it further

Find 468+257 and check with subtraction. Expected: 725; 725−257=468.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.