Numbers to 1 000

Three floors of a number: hundreds, tens, ones

So far we have counted to a hundred. Now we move the border: to a thousand.

Every number to 1 000 has three floors. Take the number 372:

• 3 means three hundreds — 300,
• 7 means seven tens — 70,
• 2 means two ones — 2.

Together 300 + 70 + 2 = 372. That writing-out is called splitting a number and it is an X-ray: it shows what is really in the number.

The important thing is the place of the digit. A three in the number 372 means three hundred, but a three in the number 723 means only thirty and in 237 a mere three. Same digit, different floor, different value.

Why do we do this right now? Because in a few lessons you will start calculating big numbers in writing under each other — and there you add exactly the floors: ones with ones, tens with tens. Whoever does not know the floors, calculates blind.

Sofie saved all year and with mum she counts the piggy bank. They take out notes and coins and sort them into piles: two hundreds, five ten-crown coins, three crowns. Mum asks: “So how much do you have?” Sofie writes on paper: 200 + 50 + 3 = 253 Kč. Then mum hides the piles and shows only the write-up “253”. “Can you tell from that how many hundreds there are?” Sofie points at the two. “And ten-crown coins?” The five. A piggy bank is really splitting a number live — each pile one floor.

How to read, split and compare

Splitting a number:

1. Read the digit in the hundreds place and add two zeros: 6 in the number 645 → 600.
2. The tens digit with one zero: 4 → 40.
3. Ones as they are: 5.
4. Write: 645 = 600 + 40 + 5.

Watch for a zero inside. The number 405 has 4 hundreds, 0 tens and 5 ones: 400 + 5. Zero holds the place — if you left it out, 45 would be left and that is a completely different number. A zero in the middle must not get lost.

Comparing two numbers:

1. Compare the hundreds. Who has more hundreds is bigger: 512 against 489 → 5 hundreds beat 4, done, 512 > 489.
2. Same hundreds? Compare the tens: 512 against 521 → hundreds the same (5), tens 1 against 2 → 521 is bigger.
3. Same tens too? The ones decide.

The sign > means “is greater than” and < “is less than”. The point always points at the smaller number — like a beak that wants to peck the smaller one.

Splitting and putting together

Splitting: the number 738.

• hundreds: 7 → 700
• tens: 3 → 30
• ones: 8 → 8

Write-up: 738 = 700 + 30 + 8.

Putting together (the other way): what is 500 + 90 + 2?

Five hundreds, nine tens, two ones → 592.

And a floor check: in 592, 5 shows hundreds, 9 tens, 2 ones. It fits.

Zero holds the place

The number 405:

• hundreds: 4 → 400
• tens: 0 → nothing, but it holds the place
• ones: 5 → 5

Splitting: 405 = 400 + 5.

Compare: 405 and 450. Both have 4 hundreds. Tens: 0 against 5 → 450 > 405.

And now a trick: 405 and 45. They look similar, but 405 has 4 hundreds and 45 has none. A zero in the middle turns forty-five into four hundred and five.

Sorting three numbers

Sort from smallest: 612, 621, 599.

Step 1: hundreds: 6, 6, 5. The number 599 has the fewest hundreds → it is the smallest.

Step 2: 612 and 621 are left. Hundreds the same (6). Tens: 1 against 2 → 612 < 621.

Result: 599 < 612 < 621.

Notice: 599 looks “big”, because it has all nines. But the hundreds floor decides before you even look at the nines.

Practice: now you do it 🎲

Now try it for real. You will see all the questions at once, like on paper. Start with ten. When it goes well, add more.

Revise adding and subtracting — now already with three-digit numbers. Splitting into floors will help you.

Practise the questions

On paper

Splitting, putting together, comparing. Write the floors under each other so you can see them.

1. Split into hundreds, tens and ones: 256, 703, 990, 111.

2. Put the numbers together: 300 + 20 + 7, 800 + 6, 400 + 90.

3. Fill the sign > or <: 456 ☐ 465, 700 ☐ 698, 320 ☐ 302.

4. Write with three digits: the biggest number from the digits 3, 8, 1 (use each once) and the smallest number from the same digits. (Watch: a number must not start with zero — there is none here, so go for it.)

Now you 💪

1. You split 738 into 700 + 30 + 8 without hesitating.
2. You know what zero does in the number 405, and you read it correctly out loud.
3. You compare two three-digit numbers by the method hundreds → tens → ones.

What to take from this lesson

• A number to 1 000 has three floors: hundreds, tens, ones. 372 = 300 + 70 + 2.
• The value of a digit depends on the place: a three can be 3, 30 or 300.
• A zero inside a number holds the place and must not get lost: 405 ≠ 45.
• Compare from the top: first hundreds, then tens, then ones.
• Money in a piggy bank is splitting a number live.

© 2026 Ing. Martin Polak / AlgoRhino · Content usage terms