Class 2 — Mathematics

Shapes: 2D and 3D, Edges and Corners

Class 2

✓By the end of this lesson students will be able to identify and name common 2D shapes (square, rectangle, triangle, circle).
✓By the end of this lesson students will be able to identify and name common 3D shapes (cuboid, cube, cylinder, cone, sphere).
✓By the end of this lesson students will be able to count the number of sides (edges) and corners of 2D shapes.
✓By the end of this lesson students will be able to count the number of edges and corners of 3D shapes.
✓By the end of this lesson students will be able to differentiate between 2D and 3D shapes.

Key concepts

2D Shapes (Flat Shapes)

2D shapes are flat shapes that can be drawn on a piece of paper. They only have length and breadth. We can see them, but we cannot hold them like solid objects. Common 2D shapes are Square, Rectangle, Triangle, and Circle.

3D Shapes (Solid Shapes)

3D shapes are solid shapes that take up space. They have length, breadth, and height. We can hold them in our hands. Common 3D shapes are Cuboid, Cube, Cylinder, Cone, and Sphere.

Edges

For 2D shapes, edges are the straight lines that form the boundary of the shape. We also call them 'sides'. For 3D shapes, edges are the lines where two flat surfaces (faces) meet.

Corners

For 2D shapes, corners are the points where two sides meet. We also call them 'vertices'. For 3D shapes, corners are the points where three or more edges meet.

Key facts to remember

12D shapes are flat, while 3D shapes are solid.
2A Square has 4 equal sides and 4 corners.
3A Rectangle has 4 sides (opposite sides are equal) and 4 corners.
4A Triangle has 3 sides and 3 corners.
5A Circle is round and has no straight sides or corners.
6A Cube has 12 edges and 8 corners.
7A Cuboid has 12 edges and 8 corners.
8A Cylinder has 2 circular edges and no corners.
9A Cone has 1 circular edge and 1 corner (at the top).
10A Sphere has no edges and no corners.

Worked examples

Example 1

Look at the given shape (imagine a drawing of a triangle). What is its name? How many sides does it have? How many corners does it have?

IStep 1: Observe the shape carefully. It has three straight lines and three points where the lines meet.

IIStep 2: Count the straight lines. There are 3 straight lines.

IIIStep 3: Count the points where the lines meet. There are 3 such points.

IVStep 4: Recall the name of the shape with 3 sides and 3 corners.

Answer

Name: Triangle. Number of sides: 3. Number of corners: 3.

Example 2

Identify the given 3D shape (imagine a drawing of a cube). How many edges does it have? How many corners does it have?

IStep 1: Observe the solid shape carefully. It looks like a dice.

IIStep 2: Count the lines where two flat surfaces meet. Carefully count all the edges. There are 12 edges.

IIIStep 3: Count the points where edges meet. Carefully count all the corners. There are 8 corners.

IVStep 4: Recall the name of this solid shape.

Answer

Name: Cube. Number of edges: 12. Number of corners: 8.

You can use a real dice to count its edges and corners.

Example 3

A matchbox is an example of which 3D shape? How many edges and corners does it have?

IStep 1: Think about the shape of a matchbox. It is a solid object with flat rectangular surfaces.

IIStep 2: This shape is called a Cuboid.

IIIStep 3: Imagine or draw a cuboid. Count its edges (the lines where surfaces meet). A cuboid has 12 edges.

IVStep 4: Count its corners (the points where edges meet). A cuboid has 8 corners.

Answer

A matchbox is an example of a Cuboid. It has 12 edges and 8 corners.

Common mistakes

✗Confusing 2D shapes with 3D shapes (e.g., calling a square a cube).
✗Incorrectly counting edges or corners, especially for 3D shapes, by missing some or counting some twice.
✗Forgetting that a circle has no straight sides or corners.
✗Confusing a cube (all square faces) with a cuboid (rectangular faces, not all square).

Exam tips

★Always look carefully at the shape before naming it.
★Use your finger to trace the sides/edges and corners to count them accurately.
★Practice identifying real-life objects that look like different 2D and 3D shapes.
★Remember the key difference: 2D shapes are flat, 3D shapes are solid and can be held.

Ready to practise?

Try a problem on this topic

Snap a photo or type a question — get step-by-step working instantly.

Solve a problem →← Maths curriculum