The idea, step by step
Find the two nearby multiples
To round to the nearest hundred, locate the number between two multiples of 100. For 3,620, the bounding hundreds are 3,600 and 3,700. The number is 20 from 3,600 but 80 from 3,700, so it is closer to 3,600.
At an exact halfway point, use the usual school rule of rounding up. Therefore 3,650 rounds to 3,700. Change the rounding place if needed, then replace lower places with zeros.
Choose a useful estimate
An estimate is approximate. Round to places that make the calculation easy while still giving useful information. For 396 × 21, use 400 × 20 = 8,000 as a quick estimate.
Do not present an estimate as the exact answer. Different rounding choices can produce different useful estimates; explain your choice. If the situation needs an exact total, calculate it after estimating.
A common trap
Rounding removes the digits to the right.
Instead: For whole numbers, replace the lower places with zeros. The nearest hundred to 6,482 is 6,500, not 65.
See the thinking
Round at a boundary
Round 9,950 to the nearest hundred.
- The bounding hundreds are 9,900 and 10,000.
- 9,950 is halfway, so round up. The carry changes the number of digits.
Estimate an addition
Estimate 1,923 + 3,078 by rounding each amount to the nearest thousand.
- 1,923 rounds to 2,000; 3,078 rounds to 3,000.
- Add the rounded amounts: 2,000 + 3,000 = 5,000.
Check your understanding
Round 28,449 to the nearest thousand.
Show answer
28,000
28,449 is below the halfway point 28,500, so it is closer to 28,000.
Your turn
6 questions · 8 marks · Work at your own pace.
Read the questions online
- Round 64,783 to the nearest thousand.1 mark
- Round 11,849 to the nearest hundred.1 mark
- Round 195 to the nearest ten.1 mark
- Estimate 396 × 21 using nearby multiples of ten or one hundred.2 marks
- Estimate 448 + 251 by rounding each amount to the nearest hundred.1 mark
- Find the smallest and largest whole numbers that round to 5,600 to the nearest hundred.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Round 64,783 to the nearest thousand.1 mark
64,783 is above 64,500, so round up.
65,000 - Round 11,849 to the nearest hundred.1 mark
11,849 is below the halfway point 11,850.
11,800 - Round 195 to the nearest ten.1 mark
195 is halfway between 190 and 200; round up.
200 - Estimate 396 × 21 using nearby multiples of ten or one hundred.2 marks
396 is about 400 and 21 is about 20; 400 × 20 = 8,000.
About 8,000 - Estimate 448 + 251 by rounding each amount to the nearest hundred.1 mark
448 rounds to 400; 251 rounds to 300; 400 + 300 = 700.
About 700 - Find the smallest and largest whole numbers that round to 5,600 to the nearest hundred.2 marks
5,550 is the first whole number rounding up to 5,600. At 5,650 the rounded answer changes to 5,700.
5,550 and 5,649
Curriculum reference & lesson scope
Australian Curriculum v9; SA Curriculum Mathematics 2026
Whole-number revision; partitioning; rounding/estimating quantities; checking reasonable answers.
Official curriculum source ↗