LEARN · PRACTISE · DISCOVER

Round and Estimate to Check

Read at your own pace. Try the practice, then continue your course.

Round numbers to a useful place, estimate sums and differences, and use the estimate to check an exact answer.

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THE CURIOSI · EXPLORE & TRY

Explore the model, then test your understanding. Select each numbered stop to discover its role.

Strategy model: follow the labelled quantities and explain each change. Number-line jumps are schematic.

1Round to useful numbers

198 is close to 200 and 304 is close to 300.

2Make an estimate

The estimate is 500. It is approximate, not an exact equality.

3Compare with the exact result

The exact sum 502 is near 500. An estimate can reveal a large error but does not prove an answer correct.

Choose a strategy you can explain. Check the numbers and include units where needed.

Choose one answer for each question, then check. Practice results stay on this page and do not change course completion.

1. 368 rounded to the nearest hundred is… 300 370 400

2. Estimate 198 + 304 by rounding to hundreds. 600 500 502

3. Does a close estimate prove the exact calculation is correct? No; check the calculation too Yes, always Only if the estimate is larger

Read the answer explanations

368 is closer to 400 than 300.
200 + 300 gives an estimate of 500; 502 is the exact result.
Different nearby numbers can fit an estimate; use an inverse or a second calculation as well.

Focus on understanding before speed. Use paper, counters or a spoken explanation whenever they help you keep track.