Decimal numbers: koruna and hellers

You already know a number with a point

Look at a price tag in a shop: a roll for 3.50 Kč. That number with a point is a decimal number. You use it every day, you just do not call it that.

The point splits the number into two parts. Before the point are the wholes — whole korunas. After the point are parts of a whole — hellers, which are hundredths of a koruna.

Until now you counted with whole numbers: 1, 2, 17, 350. But the world is not only wholes. Half a litre of milk, a metre and a bit of fabric, a race time to seconds and tenths. For that you need numbers between whole numbers.

The first place after the point is tenths — a whole split into 10 parts. The second place is hundredths — a whole into 100 parts. So 24.90 means: 24 wholes, 9 tenths, 0 hundredths.

In this level you become a Fraction kid: you will handle decimals, fractions, angles and boxes. We start with money, because you already know that.

Ema stands at the till with a fifty-koruna note in her hand. The shopping: a roll 3.50 Kč, yoghurt 12.90 Kč. “How much is that together?” asks Adam. Ema shrugs: “Thirteen… something?” The cashier smiles: “16.40.” Ema stares at the receipt. She could read those numbers with a point, but she could not add them. At home she takes paper: 3.50 is 3 korunas and 50 hellers. 12.90 is 12 korunas and 90 hellers. Korunas apart, hellers apart — and suddenly it makes sense. That is exactly what you will learn now.

💡

When you are stuck with a decimal number, turn it into money in your head. 0.5 = fifty hellers, so half a koruna. Your brain already knows money.

What each digit says

Take the number 24.90 and break it into pieces:

Place	Digit	Means
tens	2	20
ones	4	4
point	.	wholes end here
tenths	9	9/10, so 0.9
hundredths	0	nothing

How to read the number out loud: “twenty-four point ninety” or “twenty-four and ninety hundredths”. In a shop you say “twenty-four ninety” — both are fine.

An important rule: a tenth is 10× more than a hundredth. Just as a ten-koruna coin is 10× more than a koruna. So 0.5 (5 tenths) is more than 0.05 (5 hundredths) — even though both numbers contain a five.

And one more rule: a zero at the end after the point changes nothing. 2.5 and 2.50 are the same number. Fifty hellers is still half a koruna, however you write it. A zero between the point and a digit changes everything: 2.05 is not 2.5.

In English we write a decimal point. A Czech price tag uses a comma (2,5) — it is the same number, just a different habit.

Break up the number 3.47

Go from the point:

Before the point: 3 wholes.
First place after the point: 4 tenths, so 0.4.
Second place after the point: 7 hundredths, so 0.07.

Write: 3.47 = 3 + 0.4 + 0.07.

Check with money: 3 korunas + 40 hellers + 7 hellers = 3 korunas and 47 hellers. It fits. You read it “three and forty-seven hundredths”.

Write “two korunas and fifty hellers” as a number

Korunas are wholes: 2. Then a point.

There are 50 hellers — and hellers are hundredths of a koruna. Fifty hundredths you write as 50 after the point.

Result: 2.50 Kč. You can also write 2.5 — a zero at the end changes nothing. Fifty hundredths is the same as 5 tenths: 50 hellers is half a koruna, and 5 tenth-pieces of a koruna is also half a koruna.

Where on the number line does 2.7 sit?

Draw a line from 2 to 3. Split it into 10 equal ticks — each tick is one tenth.

The number 2.7 sits on the seventh tick from two. It is closer to three than to two, because 7 tenths is more than a half (5 tenths).

You find 2.35 the same way: it is between 2.3 and 2.4, right in the middle of that small tick. The number line is a map — every decimal number has its place on it.

⚠️

0.5 is not “zero point five hundredths”. The five right after the point is tenths, not hundredths. 0.5 = a half. 0.05 = five hundredths, so ten times less. Who mixes this up then mixes everything else — always read the digits after the point by their places.

Practice: now you do it 🎲

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

Practise length conversions. Metres and centimetres work the same as wholes and hundredths — 1 cm is a hundredth of a metre. Write the answer as a number.

Practise the questions

On paper

Take a pencil and an old receipt (or make the prices up).

Write three shop prices under each other, for example 12.90, 4.50 and 129.00. On each one circle the wholes and underline the part after the point.
Break up the number 6.38 like in the first example: wholes + tenths + hundredths. Write it as a sum of three numbers.
Draw a number line from 0 to 1, split it into 10 ticks and mark 0.3, 0.5 and 0.9 on it.
Write three pairs of numbers that look different but are the same — for example 2.5 and 2.50. By each pair write why they are the same.

Now you 💪

I can read 7.25 out loud and I know what is the whole, what is tenths and what is hundredths.
I can explain why 0.5 is more than 0.05 — for example with hellers.
I can find 2.7 on the number line between 2 and 3 without counting ticks from zero.

✅

Done when: You break up any number with two places after the point into wholes, tenths and hundredths — and you can read it out loud correctly.

What to take from this lesson

The decimal point splits wholes from parts of a whole. Before the point korunas, after the point hellers.
The first place after the point is tenths (a part of 10), the second hundredths (a part of 100).
A tenth is 10× more than a hundredth — 0.5 > 0.05.
A zero at the end after the point changes nothing: 2.5 = 2.50. A zero right after the point changes everything: 2.05 ≠ 2.5.
In English we write a point, Czech shops often write a comma. It is the same number.