Understanding Elementary Shapes Class 6 Notes: Chapter 5

Understanding elementary shapes class 6 notes is one of the most handy resources for the students studying in CBSE class 6. These notes are given in a simple and concise way and are easily understandable. These chapter 5 maths notes will not only help class 6 students to learn various important topics from this chapter easily but will also help them to revise efficiently.

Understanding Elementary Shapes Introduction

This chapter mostly deals with the measuring of line segments, about angles and its types, about triangles and their classifications, polygons, quadrilaterals, and solid shapes. All these topics are explained in detail below.

Measuring Line Segments

A ruler or a divider is generally used to find the lengths of line segments. The length of a line segment can be defined as the distance between its endpoints.

Angles and its Types

An angle is made up of any two rays which have the same endpoint or starting point. It can be better understood from the movement of clock-hands. When a clock hand moves, it forms an angle. To measure angle, a protractor is used. It should be noted that a straight angle is 180 degrees while a right angle is 90 degrees.

Based on the degree, an angle can be classified into 3 main types:

  • Acute angle: When an angle measure is less than a right angle, it is called an acute angle.
  • Obtuse angle: When an angle measure more than a right angle but less than a straight angle, it is called an obtuse angle.
  • Reflex angle: When an angle measure more than a straight angle, it is called a reflex angle.

It should be noted that two intersecting lines are perpendicular if the angle formed between them is 90 degrees.

Triangles and its Types

A triangle is a closed figure having three sides and three interior angles. A triangle can be classified based on its length of sides and by its angles. The detailed classification of triangles is given below.

Based on Triangle Name Description

Based on its sides

Scalene triangle All three sides are unequal.
Isosceles triangle Any two sides are equal.
Equilateral triangle All three sides are equal.

Based on its angles

Acute angled triangle All the angles are acute.
Right angled triangle Any one angle is right angle.
Obtuse angled triangle Any one angle is obtuse.


Polygons are closed geometric shapes having at least 3 sides and 3 angles. Based on the number of sides, a polygon can be categorised into multiple types. Some of most common polygons are-

Polygon Name No. of Sides
Triangle 3
Quadrilateral 4
Pentagon 5
Hexagon 6
Heptagon 7
Octagon 8
Nonagon 9
Decagon 10


As mentioned in the table above, a quadrilateral is one of the types of polygons having 4 sides and 4 angles. A quadrilateral can be categorised into 5 main types which are explained below.

Quadrilateral Type Property
Rhombus It has 4 sides of equal length.
Square It is rhombus with 4 right angles.
Parallelogram It has two pairs of parallel sides.
Rectangle It is a parallelogram of 4 right angles.
Trapezium It has one pair of parallel sides.

Solid Shapes or 3D Shapes

A solid shape or three dimensional shape (3D shape) can be defined as the objects which can be measured in three directions i.e. length, breadth, and height. Examples of 3d shapes are cylinder, cube, cuboid, sphere, etc. Check out three dimensional shapes to learn more about them and to get acquainted with the terms related to them.

Practice Questions

  1. Determine the type of triangle if its sides are of 7 cm, 8 cm, and 9 cm.
  2. What kind of angle is one whose measure is the sum of the measures of two right angles?
  3. Is it possible to draw an obtuse angled equilateral triangle? Justify.
  4. What shape does a match box has if its sides are equal?

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Practise This Question

Which is the equivalent fraction of 1218?