Geometry — Class 1 Mathematics (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 1 Mathematics, Chapter 1. Shapes and Spaces.
1. Shapes are all around you
Look at the clock on your classroom wall. It is round. Look at the door you walked through. It is long and straight on all four sides. Look at your tiffin box. It is a box you can hold.
Every object has a shape. In this chapter we learn the names of shapes, so that instead of saying "the round thing", you can say "the circle".
Shapes come in two families. Some shapes are flat — you can draw them on paper with a pencil. Some shapes are solid — you can pick them up and hold them in your hand.
2. Flat shapes you can draw
A flat shape has only length and width. It has no thickness. You cannot hold a circle; you can only draw one.
| Shape | Sides | Corners | Where you see it |
|---|---|---|---|
| Circle | 0 (one curved line) | 0 | Clock face, ₹1 coin, bangle, chapati |
| Square | 4 equal sides | 4 | Carrom board, chess board, a slice of bread |
| Triangle | 3 sides | 3 | A samosa, a sandwich cut in half, a road sign |
| Rectangle | 4 sides (2 long, 2 short) | 4 | Door, blackboard, your notebook |
A corner is the point where two sides meet. Put your finger on a square. Count the pointy places. You will count 4.
A circle has no corners at all. Run your finger around a bangle. Your finger never stops or turns. That is why a circle has zero corners.
Square or rectangle? Both have 4 sides and 4 corners, so children mix them up. The test is simple: in a square, all 4 sides are the same length. In a rectangle, 2 sides are long and 2 sides are short. A square is a special rectangle where the long and short sides happen to be equal.
3. Solid shapes you can hold
A solid shape takes up space. You can hold it, stack it, or roll it.
| Solid shape | What it looks like | Real object |
|---|---|---|
| Sphere | Round on every side | Football, laddu, marble |
| Cube | 6 square faces, all equal | Dice, sugar cube, Rubik's cube |
| Cuboid | 6 rectangle faces | Brick, matchbox, tiffin box |
| Cylinder | Two flat circles joined by a curved side | Drum, tin can, candle |
| Cone | One flat circle rising to a point | Ice cream cone, birthday cap, funnel |
Be careful with two words that sound alike. A circle is flat — you draw it. A sphere is solid — you throw it and catch it. A bangle is a circle. A football is a sphere.
4. Which ones roll, which ones slide?
Put a ball and a book on a sloping board and let both go.
The ball rolls. It has a curved surface, so it keeps turning over and over. The book slides. It has flat faces, so it slips down without turning.
- Rolls: ball, bottle, pencil, tin can, marble
- Slides: book, box, eraser, brick, tiffin box
A ₹5 coin is interesting. Stand it on its edge and push — it rolls. Lay it flat and push — it slides. A coin can do both, because it has a curved edge and two flat faces.
5. Words that tell us where
Shapes also need position words, so we can say exactly where something is.
- Near / Far — The pencil is near my hand. The gate is far from the classroom.
- Big / Small — The elephant is big. The ant is small.
- Inside / Outside — The fish is inside the bowl. The cat is outside the house.
- Above / Below — The fan is above my head. The mat is below my feet.
- Top / Bottom — Books are on the top shelf. Toys are on the bottom shelf.
6. Worked examples
Example 1. Kavi has a matchbox, a football and a dice. Which one is a cuboid?
Answer: The matchbox. It has 6 faces and each face is a rectangle. The football is a sphere and the dice is a cube.
Example 2. How many corners does a triangle have, and how many does a circle have?
Answer: A triangle has 3 corners. A circle has 0 corners, because it is made from one smooth curved line.
Example 3. Arun rolls a tin can and a chalk box down a slope. Which one reaches the bottom by rolling?
Answer: The tin can. It is a cylinder with a curved surface, so it rolls. The chalk box is a cuboid with flat faces, so it only slides.
Example 4. A shape has 4 sides. Two sides are long and two sides are short. Name it.
Answer: A rectangle. If all four sides had been equal, it would be a square.
7. Practice
- What shape is a chapati?
- How many sides does a triangle have?
- Name one object in your house that is a cylinder.
- Is a dice a cube or a cuboid?
- Does an eraser roll or slide?
- The bird is ______ the nest. (inside / outside)
- A shape has 4 equal sides and 4 corners. What is its name?
8. Answers
- Circle.
- Three sides.
- A tin of biscuits, a water bottle, or a drum.
- A cube, because all 6 faces are equal squares.
- It slides. An eraser has flat faces and no curved surface.
- Inside.
- Square.
9. Summary
- Flat shapes are drawn on paper: circle, square, triangle, rectangle.
- Solid shapes are held in the hand: sphere, cube, cuboid, cylinder, cone.
- Corners are where two sides meet. A circle has none; a triangle has 3; a square and a rectangle have 4 each.
- A square has 4 equal sides; a rectangle has 2 long and 2 short sides.
- Curved surfaces roll. Flat faces slide. A coin does both.
- Position words — near, far, inside, outside, above, below, top, bottom — tell us where a thing is.
