Shapes: square, rectangle, triangle, circle · Lập trình với Martin

Four basic shapes. You will learn to spot them, describe them and find them all around you.

The world is built from shapes

Look around. A window, a door, a wheel, a road sign. Everything has a shape. Today you will learn the four most important ones.

A square has four sides, all the same length. Like a square on school paper.

A rectangle has four sides too, but two long and two short. Like a door or a bar of chocolate.

A triangle has three sides and three points. Like the roof of a little house in a picture.

A circle is round. No side, no point. Like a wheel, a plate, a coin.

Why learn shapes? Because the world is built from them. A builder draws rectangles before building a house. Road signs have shapes on purpose: a triangle warns, a circle commands. Anyone who knows shapes reads the world around them like a book. And they can draw them too — you will learn that today as well.

The points are called vertices in maths and the lines are called sides. You spot shapes by those: you count the sides and the vertices.

Tereza and Jonáš play “find a shape”. “I see a circle!” Tereza reports and points at the clock on the wall. Jonáš: “I see a rectangle — the door!” Tereza finds a square on a chessboard, Jonáš a triangle on a road sign in front of the house. Then Jonáš wants a point for a cushion. “That is not a square, it is a soft cushion,” Tereza laughs. “But it has a square shape! Four same sides.” The point counts. The first to find ten shapes wins. Tereza leads nine to eight. The last point is decided by a round button on a coat: “Circle! Ten!” Jonáš wants a rematch at once — this time in the kitchen.

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Not sure what shape it is? Count the sides and the vertices. Three and three = a triangle. Four and four = a square, or a rectangle — the length of the sides decides.

How to spot a shape for sure

Spotting a shape has a clear method:

1. Is it round, with no corners? Then it is a circle. Done.

2. Count the vertices (points). Three vertices = a triangle. Four vertices = go to step 3.

3. Compare the sides. All four the same length = a square. Two long and two short = a rectangle.

A small interesting fact: a square is really a special rectangle that managed to have all sides the same. But at school we know them as two shapes.

Watch turning. A square stood on a point is still a square. Turning does not change a shape. Some people call it “a diamond like in cards”, but if it has four same sides and square corners, it is a turned square.

Drawing. Draw a square and a rectangle with a ruler, the corners should be as square as the corner of a notebook. A triangle: three dots, join them with a ruler. A circle is best traced — a mug or a coin works great.

Shapes are flat — they live on paper. A cube or a ball is something else, those are solids. We will look at those next time.

What shape is a bar of chocolate?

Round? No, it has corners. It is not a circle.

How many vertices? Four corners.

Sides? Two longer (top and bottom) and two shorter (on the sides).

Four vertices, sides of two lengths → a rectangle.

If all four sides were the same, it would be a square. With chocolate almost never — it is usually long.

Draw a triangle

Step 1: Make three dots on the paper. Not in one line — so they make points.

Step 2: Tham gia the first and second dot with a ruler.

Step 3: Tham gia the second and third. Then the third and first.

Done: three sides, three vertices, a triangle.

Any three dots (that do not lie in one line) make a triangle. Try it: pointy, flat, big — still a triangle.

Is a turned square still a square?

I draw a square and turn the paper so it stands on a point. It looks like a gem.

I count the vertices: still 4. I measure the sides with a ruler: still all the same.

It is a square. Turning does not change a shape.

In the same way a triangle upside down is still a triangle. You spot a shape by sides and vertices, not by how it happens to be turned.

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Do not mix a square with a rectangle. Both have four corners! The sides decide: all the same = a square, two and two = a rectangle. If you are not sure, measure them with a ruler.

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. Bắt đầu with ten. If it goes well, add more.

Tap the name of the shape. Count the sides and the corners.

Practise the questions

On paper

Paper, a pencil, a ruler and a mug for tracing a circle.

Draw all four shapes: a square, a rectangle, a triangle and a circle. Straight lines with a ruler.
For each shape write the number of sides and vertices. For the circle write what is different.
Play finding shapes: find two circles at home, two rectangles, one square and one triangle.
Draw a little house only from shapes: a square, a triangle as the roof, a rectangle door and a round window.

Now you 💪

I know a square, a rectangle, a triangle and a circle.
I can count sides and vertices.
I know that a turned shape is still the same shape.

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Done when: You draw all four shapes, describe them correctly and find them at home.

What to take from this lesson

Square: 4 same sides. Rectangle: 2 long and 2 short.
Triangle: 3 sides, 3 vertices. Circle: round, no corners.
You spot a shape by counting sides and vertices.
Turning does not change a shape.
Shapes are flat. A cube and a ball are solids — next time.