Fractions, Shapes and Data
Primary 3 · Mathematics
Fractions, Shapes and Data
Lesson 2 of 3
12 min
Let's begin
Stop reading for a moment and look around you. The window is a rectangle. The clock is a circle. The roof of a house makes a triangle. A football is round all over.
Shapes are everywhere, quietly waiting for you to name them. Let us learn their names and, even better, how to describe them.
A flat shape lies still on the page. To describe one, you only need two things:
Count the sides, count the corners, and you can name almost any flat shape.
A square has 4 straight sides and 4 corners. All 4 sides are exactly the same length. A floor tile is a square.
A rectangle also has 4 straight sides and 4 corners. But it has 2 long sides and 2 short sides. The sides facing each other are equal. The classroom door is a rectangle.
(A square is really a special rectangle: one where the long sides and the short sides happen to be the same length.)
A triangle has 3 straight sides and 3 corners. The tri in triangle means three. Look at the two slopes of a roof meeting the wall.
A circle has 1 curved edge that goes round and round with no end. It has no straight sides and no corners. The face of a clock is a circle.
Gatete looks at the classroom door and describes it out loud.
Four sides, four corners, two long and two short. It is a rectangle.
Now try the same steps on a slice of the school signboard shaped like this: 3 straight sides, 3 corners. Three sides tells you at once: it is a triangle.
A flat shape lives on paper. A solid shape takes up space in your hands. You cannot draw a real football on paper; you can only draw a picture of it.
A cube is like a dice or a sugar cube. It has 6 flat faces, and every single face is a square. It has 8 corners and 12 straight edges. Put it on the table and it stays there. A cube never rolls.
A sphere is a ball: a football, an orange, the Earth. It is round all over. It has no flat faces and no corners. Push it and it rolls away in any direction you like.
A cylinder is like a tin of tomato paste, a candle, or a drum. It has 2 flat faces (the top and the bottom, and both of them are circles) and 1 curved side wrapped around the middle. It has no corners.
| Solid | Flat faces | Corners | Does it roll? |
|---|---|---|---|
| Cube | 6 squares | 8 | No |
| Sphere | 0 | 0 | Yes, any direction |
| Cylinder | 2 circles | 0 | Yes, but only one way |
Byiringiro picks up a tin of tomato paste from the shelf. What solid shape is it?
Two flat circle faces and one curved side. It is a cylinder.
Tip
Give it a push! A box does not roll at all, so it is a cube. A tin rolls one way only, so it is a cylinder. A ball rolls every way, so it is a sphere. For flat shapes, just count: 3 sides means triangle, 4 sides means square or rectangle, no corners at all means circle.
Answer out loud, then tap Show answer to check.
How many corners does a triangle have?
Answer: 3. It has 3 sides, and every place where two sides meet is a corner, so 3 corners.
I have 4 straight sides and 4 corners. My two long sides are equal and my two short sides are equal. What am I?
Answer: a rectangle. If all four sides were the same length, I would be a square.
Which flat shape has no corners?
Answer: the circle. Its edge is one smooth curve, so no two sides ever meet.
A dice has 6 flat faces and every face is a square. Which solid is it?
Answer: a cube.
Umutoni's water drum has two flat circle faces and one curved side. Which solid is it?
Answer: a cylinder.
How many corners does a cube have?
Answer: 8. Count 4 corners on the top face and 4 corners on the bottom face: 4 + 4 = 8.
What you learned today
Quick check
Match each flat shape to its sides.
Tap one on the left, then its partner on the right.
