The idea, step by step
Find the neighbouring round numbers
To round 6,438 to the nearest hundred, place it between 6,400 and 6,500. Halfway is 6,450. Since 6,438 is below halfway, it is closer to 6,400. At an exact halfway point, use the higher hundred.
The requested place matters. For the nearest ten, use the ones digit to decide. For hundreds, use the tens digit. For thousands, use the hundreds digit. The rounded answer must be a multiple of the requested place.
Estimate, calculate, check
Round numbers to make a quick calculation manageable. For 432 + 287, rounding to hundreds gives 400 + 300 = 700. This is roughly what to expect, not the exact total.
An estimate can reveal a missing digit or an answer of the wrong size. It cannot detect every small mistake. After calculating exactly, check with another strategy or the inverse operation. Use exact counts when every item matters.
A common trap
Rounding 4,950 to the nearest hundred as 4,900 because it starts with 49.
Instead: 4,950 is halfway between 4,900 and 5,000. Round up to 5,000. Rounding can regroup digits.
See the thinking
Round at two places
Round 7,482 to the nearest ten and nearest hundred.
- For tens, it lies between 7,480 and 7,490 and is nearer 7,480.
- For hundreds, it lies above 7,450, halfway between 7,400 and 7,500.
Use an estimate
Estimate 432 + 287 to the nearest hundred, then calculate exactly.
- Round the numbers to 400 and 300: estimate 700.
- 432 + 200 + 80 + 7 = 719.
- 719 is close to 700, so the estimate supports the answer's size.
Check your understanding
Round 8,249 to the nearest hundred.
Show answer
8,200.
It is below the halfway point 8,250 between 8,200 and 8,300.
Your turn
6 questions · 9 marks · Work at your own pace.
Read the questions online
- Round 3,674 to the nearest ten.1 mark
- Round 6,450 to the nearest hundred.1 mark
- Round 7,499 to the nearest thousand.1 mark
- Estimate 386 + 512 by rounding each number to the nearest hundred.2 marks
- Estimate 1,204 − 598 to the nearest hundred, then find the exact difference.2 marks
- 2,341 and 2,349 both round to 2,300 to the nearest hundred. Does this mean they are equal? Explain.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Round 3,674 to the nearest ten.1 mark
The ones digit is 4, so the lower ten is nearer.
3,670. - Round 6,450 to the nearest hundred.1 mark
It is halfway, so use the higher hundred.
6,500. - Round 7,499 to the nearest thousand.1 mark
It is below the halfway point 7,500.
7,000. - Estimate 386 + 512 by rounding each number to the nearest hundred.2 marks
386 rounds to 400; 512 rounds to 500.
400 + 500 = 900.
900. - Estimate 1,204 − 598 to the nearest hundred, then find the exact difference.2 marks
1,200 − 600 = 600.
1,204 − 600 + 2 = 606.
Estimate 600; exact difference 606. - 2,341 and 2,349 both round to 2,300 to the nearest hundred. Does this mean they are equal? Explain.2 marks
2,349 − 2,341 = 8.
Rounding groups nearby values; it does not make them equal.
No. Their exact values differ by 8.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Place-value revision; odd/even properties; addition/subtraction strategies; missing values; rounding/checking.
Official curriculum source ↗