Primary 2 · Mathematics
P2 numbers to 1000
Ask for the number with 7 hundreds, 16 tens and 9 ones, and 7169 often comes back. Every count was copied correctly. A pile of toy $10 notes shows why 16 tens cannot sit in one place.
- Level
- P2
- Usually taught
- Term 1
- Covers
- 3 concepts
What changes at P2
In Primary 2 numbers grow to 1000. Your child reads and writes them in numerals and in words, keeping the "and" (869 is eight hundred and sixty-nine), and works with place value: hundreds, tens and ones.
The topic also covers odd and even numbers and number patterns that count on or back in equal steps, such as 3, 20 or 150. One rule runs through all of it: no place holds more than 9, so ten of anything regroups into the next place.
The sentence that costs the mark
What number has 7 hundreds, 16 tens and 9 ones?
What the working usually does
7 hundreds, 16 tens, 9 ones:write 7, 16, 9=7169
Copies each count in order, so the 16 takes up two places.
What the question asked
7 hundreds, 16 tens, 9 ones:700 + 160 + 9=869
Turns each place into its value first, then adds.
Every count was copied correctly and in order, and 7169 even contains the 7, the 16 and the 9. Only the regroup is missing. Until now, no place has ever held more than 9.
| Place | How many |
|---|---|
| Hundreds | 7 |
| Tens | 16 |
| Ones | 9 |
The same question, worked properly
Write each place as its value
7 hundreds = 700The hundreds hold a single digit, so they go straight to 700, and the 9 ones are simply 9.
Turn the 16 tens into a value
16 tens = 160This is the step that fails. Ten of those tens make another hundred, so 16 tens is 1 hundred and 6 tens. Copied down as "16", it takes two places and pushes the 7 into the thousands.
Add the values
700 + 160 + 9 = 869In words, eight hundred and sixty-nine, with the "and" that Singapore schools keep.
How can you tell it has clicked?
Ask for the number made of 4 hundreds, 28 tens and 2 ones. An answer of 4282 means the counts were copied side by side. A child who says 400 + 280 + 2, which is 682, has it.
Then ask how many tens make 250. The answer is 25. An answer of 5 means the hundreds were left out, which is the same idea read the other way.
One thing to try tonight
Lay out 16 toy $10 notes and ask what they are worth together. Then swap ten of them for one $100 note.
Ask for the amount again. It has not changed, and the pile now shows 1 hundred and 6 tens, which is the regroup the page is about.
What your child will meet in this topic
- 3-Digit Place Value
- Odd and Even Numbers
- Number Patterns
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
Adding and subtracting within 1000 comes next in P2, and the same regroup drives the column method: 13 ones become 1 ten and 3 ones.
In P3 numbers reach 10 000, and the rule does not change: no place holds more than 9.
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 2
Other topics in the same year, so you can see what sits either side of this one.
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.