Numbers to 20

After ten it keeps going

You have run out of ten fingers. And there are more sweets. What now? Nothing bad. Numbers keep going: 11, 12, 13… up to 20. And then even further, but that is for another day.

Numbers after ten have a trick. Eleven is ten and one. Twelve is ten and two. Fifteen is ten and five. You can hear it in the name: fif-teen means five and ten.

They are written with two digits. Eleven is 11. Fifteen is 15. Twenty is 20. The first digit says: I have one full ten. The second digit says how many extra there are.

Where do you meet numbers like these? Eighteen of you may sit in class. There are twenty eggs in a tray. Fingers on hands and toes on feet make twenty together too. The world is full of numbers between ten and twenty — and today you will learn to read them and write them.

Once you get this, counting to twenty is easy. It is not something new. It is ten and a bit more.

Tereza and Jonáš are building a tower of bricks. There is a big pile of bricks. “We cannot count that, there are too many,” says Jonáš. Tereza has an idea: “Let’s make a pile of ten. We count the rest on its own.” They count ten bricks onto one pile. Four are left beside it. “Ten and four… fourteen!” says Tereza. Jonáš tries counting one by one: one, two, three… fourteen. It matches! It just took much longer. From then on they always count bricks the same way: first a pile of ten, then the rest. The tower is built before mum calls them to dinner. A pile of ten saves time.

Ten and a bit more

How do you count things up to twenty? You have two paths.

Path one: one by one. One, two, three… all the way to the end. It always works. But with big piles it is easy to slip.

Path two: through ten. You do it like this:

1. Count exactly ten things onto one pile.
2. Put the rest beside it and count them. Maybe you get three.
3. Say: ten and three is thirteen.

The names of the numbers help you. Thir-teen = three and ten. Four-teen = four and ten. Six-teen = six and ten. Only eleven and twelve do not give it away so clearly. You have to remember those two.

And the writing? Thirteen is written 13. The one at the front means one ten. The three at the back is three extra. Twenty is written 20 — that is two full tens and nothing extra.

Try saying the numbers from 1 to 20 out loud. There and then backwards. Backwards is harder, but it is a great way to learn the numbers.

How many beans?

There is a pile of beans on the table. It looks huge.

Step 1: I count ten beans and put them on the left. One, two… ten. Done.

Step 2: I count the rest. One, two, three, four, five, six. Six extra beans.

Step 3: Ten and six is sixteen. I write 16.

Check with the name: six-teen. Six and ten. It matches.

Write the number nineteen

Nineteen. Do you hear nine-teen? Nine and ten.

So: one ten and nine extra.

I write the one first, for the ten: 1. Then the nine for the extra: 9. Together 19.

And the other way: I see 14 written down. One ten and four extra. Ten and four — fourteen. I can read a number and write it.

Play it

Before you go to the sheet, try it with your eyes. This is not a test — it is a game. Tap until you see it.

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. If it goes well, add more.

Numbers to 20 live on the number line. Who is the neighbour?

Practise the questions

On paper

You need paper, a pencil and a pile of small things — beans, buttons, pasta.

1. Write the numbers from 10 to 20 in a row. Say them out loud.

2. A parent tips a pile of things for you (between 11 and 20). Count ten aside, count the rest and write the whole number.

3. Write these numbers as a parent says them: thirteen, seventeen, eleven, twenty.

4. Try saying the numbers from 20 to 1 backwards. Slowly is fine.

Now you 💪

1. I can count from 1 to 20 with no mistake.
2. I know that fifteen means ten and five.
3. I can write numbers like 13, 17 or 20 and I do not mix up the order of the digits.

What to take from this lesson

• Numbers after ten: 11 to 20.
• Fifteen = ten and five. The name gives it away.
• The first digit is the ten, the second is the extra.
• Count a big pile through a pile of ten.
• 12 and 21 are not the same numbers. Order decides.

© 2026 Ing. Martin Polak / AlgoRhino · 内容使用条款