Understand the idea.
Choose the required place
To round, first identify the place you will keep. Inspect the next digit: 0–4 keeps the retained digit unchanged, while 5–9 increases it by one. Later whole-number places become zero placeholders.
Rounding selects the nearest multiple of the stated place value, with halfway values rounded up here. Use to mark the approximation. Always state the place: the nearest hundred and the nearest thousand answer different questions.
Estimate with convenient numbers
An estimate uses nearby convenient numbers to predict the size of a calculation. Choose values whose arithmetic you can do confidently. State those choices so someone else can judge whether your approximation is useful.
Keep estimation separate from the exact calculation. Their results should be reasonably close, not necessarily equal. Context also matters: an estimate rounded down may be unsuitable when you must guarantee enough money, seats or materials.
See the method in action.
Round to a stated place
Round 48,762 to the nearest thousand.
Worked solution
- 1
Identify the neighbouring thousands.
Rounding to the nearest thousand chooses between these two multiples of 1,000.
- 2
Inspect the hundreds digit.
The hundreds digit is at least 5, so the number is nearer the upper thousand.
- 3
Write the rounded value.
The thousands increase by one and the later places become zero.
49,000
Check a product with an estimate
Estimate , then compare with the exact product.
Worked solution
- 1
Choose nearby convenient factors.
Four hundred times twenty is easy to calculate mentally.
- 2
Calculate the estimate.
The estimate gives a target size for the exact product.
- 3
Calculate the exact product.
Splitting 21 into 20 and 1 preserves the exact calculation.
- 4
Compare the two results.
A difference of 127 is small compared with a total near 8,000, so the estimate supports the result’s size.
An estimate is 8,000; the exact answer is 8,127.
Try it yourself.
Check your understanding
Round 7,250 to the nearest hundred.
Show answer & reasoning
7,300
In 7,250 the tens digit is 5, so this halfway value rounds up from 72 hundreds to 73 hundreds: to the nearest hundred.
Keep practising
6 worksheet questions · 13 marks
Read the questions online
- Round 34,876 to the nearest hundred.2 marks
- Round 96,450 to the nearest thousand.2 marks
- Estimate using convenient whole numbers.2 marks
- Estimate using convenient whole numbers.2 marks
- There are 51 tickets at 19 dollars each. Estimate the total, then find the exact cost.3 marks
- Round 4,650 to the nearest thousand.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Round 34,876 to the nearest hundred.2 marks
Keep the hundreds position.
The tens digit is 7, so round 8 hundreds up to 9 hundreds.
34,900 - Round 96,450 to the nearest thousand.2 marks
The hundreds digit is 4.
Keep 96 thousands and replace the later digits with zeros.
96,000 - Estimate using convenient whole numbers.2 marks
Use and .
.
About 6,000 - Estimate using convenient whole numbers.2 marks
Use and .
.
About 30 - There are 51 tickets at 19 dollars each. Estimate the total, then find the exact cost.3 marks
Estimate with .
Calculate .
Estimate: 1,000 dollars; exact cost: 969 dollars. - Round 4,650 to the nearest thousand.2 marks
The hundreds digit is 6.
Round 4 thousands up to 5 thousands.
5,000
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum
Place value and powers of ten; efficient whole-number calculations and order of operations; factors, multiples and primes; prime factorisation and exponent notation; square numbers and square roots; estimation and rounding.
Official curriculum source ↗