Even and odd numbers · البرمجة مع مارتن

Which number splits into pairs and which does not? You will spot even and odd numbers at once.

Line up in pairs!

Six children sign up for a trip in pairs. They line up in pairs and nobody is left over. Six is an even number.

Seven children? Three pairs and one child is left over. Seven is an odd number.

That is the whole secret. An even number splits into pairs with nothing left. An odd one does not — one is always left over.

Even numbers to ten: 2, 4, 6, 8, 10. Odd: 1, 3, 5, 7, 9. They take turns nicely: odd, even, odd, even…

What is it for? You need pairs all the time. Split the class into pairs. Share sweets fairly between two children. Put players into two teams. An even number means: it comes out exactly. An odd number means: someone is left over and it has to be solved another way. So it helps to spot it in advance — and you can do it with one look.

And zero? Zero is even. Nobody was left over, because nobody came.

The teacher lines the class up in pairs for swimming. “There are 19 of us today,” Tereza reports. Filip shouts at once: “That will not work! Nineteen is odd.” The teacher smiles: “How do you know so fast?” Filip: “It ends with a nine. Nine is odd, so the whole number is odd.” Really: nine pairs and Tereza is left over. “I’ll go with the teacher,” Tereza laughs. On the way back there are 20 of them — a latecomer arrived. Even. The pairs come out exactly. From then on Filip counts pairs everywhere: stairs, buttons, bus windows. “Nineteen stairs. Odd!” he reports at home. Mum just smiles.

💡

With big numbers only the last digit decides. It ends with 0, 2, 4, 6, 8 → even. It ends with 1, 3, 5, 7, 9 → odd.

How to spot even and odd

Small numbers you spot with pairs. Take bricks and put them into pairs:

8 bricks: four pairs, nothing left. Even.
5 bricks: two pairs and one brick left. Odd.

Big numbers you spot by the last digit. You do not have to pair 74 bricks. Just look at the end of the number:

74 ends with a four. Four is even → 74 is even.
61 ends with a one. One is odd → 61 is odd.

Why does it work? Tens always split into pairs (ten is five pairs). Only the ones at the end decide the result.

Taking turns. On the number line, even and odd take turns like tiles: 1 odd, 2 even, 3 odd, 4 even… The neighbour of an even number is always odd and the other way round.

Where does it help? Splitting into pairs, games (even and odd numbers on a dice), house numbers — on one side of the street they are often even, on the other odd. Have a look on your street.

Is 14 even or odd?

Pairs path: 14 bricks. I put them: 2, 4, 6, 8, 10, 12, 14 — seven pairs, nothing left. Even.

Last-digit path: 14 ends with a four. Four is even.

Both paths say: 14 is even.

Fourteen children split into seven pairs and nobody is left over.

Is 87 even or odd?

I will not pair eighty-seven bricks. I look at the end.

87 ends with a seven. Seven is odd: three pairs and one left over.

So 87 is odd.

The tens do not interest me — eight tens always split into pairs. Only that seven at the end decides.

Even and odd in a row

I write the numbers 10 to 20 and mark them:

10 even, 11 odd, 12 even, 13 odd, 14 even, 15 odd, 16 even, 17 odd, 18 even, 19 odd, 20 even.

They take turns completely regularly. Not once are two even or two odd next to each other.

So it is enough to know one and you can work out the neighbours: if 14 is even, 15 must be odd.

⚠️

Do not look at the first digit! With the number 25 the two does not decide, but the five at the end. 25 is odd, even though it starts with an even two.

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. البداية with ten. If it goes well, add more.

Dots into pairs. Even or odd?

Practise the questions

On paper

Paper, a pencil and a handful of bricks or beans.

Take 9, 12 and 15 beans (one after another) and split them into pairs. Write what is even and what is odd.
Write the numbers 1 to 20. Circle even ones in blue, odd ones in red. Do you see the taking turns?
Decide only by the last digit: 34, 47, 90, 61, 78.
Find out if your house number is even or odd.

Now you 💪

I know that an even number splits into pairs with nothing left.
With a big number I decide by the last digit.
I know that even and odd numbers take turns on the line.

✅

Done when: You decide correctly about ten numbers to a hundred, whether they are even or odd.

What to take from this lesson

Even = the pairs come out exactly. Odd = one is left over.
Even digits: 0, 2, 4, 6, 8. Odd: 1, 3, 5, 7, 9.
With big numbers only the last digit decides.
Even and odd take turns like tiles.
Zero is even.