Understand the idea.
Find the two nearby multiples
Rounding replaces a number with a nearby multiple of a chosen place. To round to the nearest hundred, compare and . The distances are and , so is nearer.
The halfway point between those hundreds is . Use the school convention: an exact halfway value rounds up. After choosing the nearest hundred, keep zeros in the tens and ones places; the rounded number must still name a whole number of hundreds.
Choose a useful estimate
An estimate uses easy nearby numbers to predict the size of a result. For , using gives a quick guide. Choose the rounding place to suit the question, rather than always rounding to the same place.
Use “about” or to show an approximation. Rounding both amounts up can make an estimated sum too large; rounding both down can make it too small. A close estimate is useful, but it does not replace an exact calculation when one is required.
See the method in action.
Round at a boundary
Round 9,950 to the nearest hundred.
Worked solution
- 1
Find the neighbouring hundreds.
The nearest hundred must be one of these two multiples of 100.
- 2
Compare the two distances.
Equal distances put 9,950 exactly halfway.
- 3
Apply the halfway rounding rule.
The school convention rounds halfway values up, including across a place-value boundary.
10,000
Estimate an addition
Estimate 1,923 + 3,078 by rounding each amount to the nearest thousand.
Worked solution
- 1
Round the first amount to the nearest thousand.
1,923 is above the halfway point 1,500.
- 2
Round the second amount to the nearest thousand.
3,078 is below the halfway point 3,500.
- 3
Add the rounded amounts.
Adding estimates gives an estimated sum of about 5,000.
- 4
Compare with the exact sum.
The exact total is one above the estimate; 5,000 remains an approximation.
About 5,000; the exact sum is 5,001.
Try it yourself.
Check your understanding
Round 28,449 to the nearest thousand.
Show answer & reasoning
28,000
The neighbouring thousands are and , with halfway point . Since , the nearest thousand is .
Keep practising
6 worksheet questions · 8 marks
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 using nearby multiples of ten or one hundred.2 marks
- Estimate 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 using nearby multiples of ten or one hundred.2 marks
396 is about 400 and 21 is about 20; .
About 8,000 - Estimate by rounding each amount to the nearest hundred.1 mark
448 rounds to 400; 251 rounds to 300; .
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 ↗