Primary 4 · Mathematics
P4 four operations of whole numbers
Rounding 4,567 to the nearest hundred turns on a single digit, the tens, and chopping the rest off instead lands on the wrong hundred. Here is which digit decides, and how to check it.
- Level
- P4
- Usually taught
- Term 1
- Covers
- 3 concepts
What changes at P4
In Primary 4, your child works with all four operations on bigger whole numbers, and a large part of the topic is rounding and estimating: swapping a number for the nearest tidy value to check that an answer is sensible.
The skill that carries the marks is knowing which digit decides the rounding. To round to a place, you look at the digit just to its right, not the place itself, and you round it, you do not simply chop off the rest.
The sentence that costs the mark
Round 4,567 to the nearest hundred.
What the working usually does
cuts off4,567=4,500
Keeps the hundreds and drops the 67, which feels like rounding down. But chopping the rest off is not the same as rounding.
What the question asked
rounds4,567=4,600
Reads the tens digit, 6, to decide. 6 is 5 or more, so the hundreds go up from 4,500 to 4,600.
4,500 is a real "nearest hundred" number, and chopping off feels like rounding down, so nothing looks careless. The only check is the deciding digit: the tens is 6, past halfway, so 4,567 rounds up, not down.
| Point | Value |
|---|---|
| 4,550 | 4550 |
| 4,567 | 4567 |
The same question, worked properly
The digit to the right decides
nearest hundred, so check the tensTo round to the nearest hundred, look at the digit just to the RIGHT of the hundreds, the tens. In 4,567 the tens digit is 6.
Five or more rounds up
6 ≥ 5, so round upThis is the step that fails. 6 is 5 or more, so the hundreds go up: 4,500 becomes 4,600. Keeping 4,500 and dropping the 67 is chopping off, not rounding, and that is where the mark goes.
Check on the number line
4,567 is past 4,5504,567 sits past the halfway point 4,550, so it is nearer 4,600. The picture and the rule agree, which is the sense-check worth doing every time.
How can you tell it has clicked?
Ask "which digit tells you whether to round up or down?" If they point to the digit to the right of the rounding place, they have it. If they point at the place itself, that is the slip.
A sense-check also works: is the number past halfway or not? Past halfway rounds up. A child who checks against the midpoint rarely chops a number off by mistake.
One thing to try tonight
At the supermarket, round each price to the nearest dollar before adding a rough total. $4.60 becomes $5, not $4. Ask "is it nearer 4 or 5?", which is the deciding-digit question out in the wild.
Estimate first, then let them work it out exactly, and compare the two. If the estimate and the answer are miles apart, one of them is wrong, and catching that is the whole reason to estimate.
What your child will meet in this topic
- Multiplying by 2-Digit
- Rounding Numbers
- Estimation
Most Singapore schools introduce this in Term 1, though schools do differ by a term either way. If your child’s school runs a different order, you can set it in the schedule on your dashboard.
What it leads to
Rounding and estimating run through every later topic: checking a long multiplication, a decimal answer, a word-problem total. Rounding first to get a ballpark is what catches a slipped digit before it costs a mark.
A child who rounds by the right digit here tends to spot their own careless answers later, when the sums are longer and a rough estimate is the only warning that something is off.
The methods your child will use here
Each one is the same method wherever it turns up, so it is worth learning once.
The same topic in other years
It comes back each year and gets harder, so it helps to see what came before and what is coming.
More in Primary 4
Other topics in the same year, so you can see what sits either side of this one.
Struggling with the working rather than the topic itself? How to help your child with problem sums
See how your child is doing on this topic
StudyLah marks each step separately, so you can see whether it was the setup or the arithmetic that cost the mark.