Mathematics · Class 6
Understanding Elementary Shapes
Types of angles, triangles, quadrilaterals, 2D and 3D shapes.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Building on basic geometry, this chapter classifies triangles and quadrilaterals, measures angles using protractor, and introduces 3D shapes — cubes, cuboids, cylinders, cones, and spheres.
Measuring Angles
- Protractor measures angles in degrees
- Acute: 0°–90°; Right: 90°; Obtuse: 90°–180°
- Reflex angle: between 180° and 360°
Types of Triangles
- By sides: scalene, isosceles, equilateral
- By angles: acute, right, obtuse
- Equilateral: all sides and angles equal (60° each)
3D Shapes
- Faces, edges, vertices (corners)
- Cube: 6 square faces, 12 edges, 8 vertices
- Cuboid: rectangular faces
- Cylinder, cone, sphere: curved surfaces
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Example 1: Triangle Classification
A triangle has sides 5 cm, 5 cm, 8 cm. Classify by sides.
- 1Two sides equal (5 cm each)
Answer
Isosceles triangle
Example 2: Faces of a Cube
How many faces, edges, and vertices does a cube have?
- 1Cube is special cuboid with square faces
Answer
6 faces, 12 edges, 8 vertices
Key Points to Remember
- ✓ Sum of angles in any triangle = 180°
- ✓ Equilateral triangle has all angles 60°
- ✓ Recognise nets of 3D solids
Exam Tips
- • Use protractor carefully — align centre with vertex
- • Name triangles by both side and angle type when possible
Practice MCQs — Understanding Elementary Shapes
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Sum of angles in a triangle is: