2
Flat or solid?
Learner’s Book 1: Unit 10, pp. 148–149
GoalSay whether a shape is 2D or 3D, and find triangles.
New words
2D shape · a flat shape3D shape · a solid shape that you can holdtriangle · a shape with 3 straight sides and 3 corners
Explanation
A 2D shape is flat. It has only length and width, like a drawing. A 3D shape is solid. You can hold it, and it has depth. A circle, a square, a rectangle and a triangle are 2D shapes. A sphere, a cube, a cylinder and a pyramid are 3D shapes. A triangle has 3 straight sides and 3 corners. Triangles can look very different, but they always have 3 sides. Small triangles can fit together to build a bigger triangle.
| 2D (flat) | 3D (solid) |
|---|---|
| circle, square, rectangle, triangle | sphere, cube, cylinder, pyramid |
Worked examples
A ball is a 3D shape. You can hold it, and it has depth.
A circle drawn on paper is a 2D shape. It is flat.
This big triangle is made from 4 small triangles. The big shape is a triangle too.
Class activity
2D or 3D hunt: find 5 flat shapes (a coin drawn on paper, a window picture, a sticker) and 5 solid shapes (a ball, a box, a cup). Say each name and sort them into two piles.
Practice
1
Is a cube a 2D shape or a 3D shape?
3D
2
Is this shape 2D or 3D?
2D (it is flat)
3
How many triangles can you see?
2 triangles and 3 other shapes.
4
How many straight sides does a triangle have?
3