One of the best resources for CBSE class 6 students is Understanding Elementary Shapes class 6 notes. The notes are written in a simple and concise manner and are easily understandable. Chapter 5 Math notes will not only provide students with the knowledge they need to learn from this chapter easily but will also assist them with revising effectively.
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Understanding Elementary Shapes Class 6 Chapter 5 Maths Notes
In this chapter, you will learn about how to measure line segments, how to differentiate angles, how to differentiate triangles, polygons, quadrilaterals, and solid shapes. All these topics are explained below:
Measurement of Line Segment:
- A line segment is defined as a segment of a line that is fixed in place. This enables the measurement of a line segment.
- The length of a line segment is the distance between its endpoints.
- When comparing the lengths of line segments, a graduated ruler and a divider are used. These methods give accurate length distances.
- Also, we can compare the two line segments by observation or with the help of trace paper. But, both the methods have a very little accuracy and we can’t trace the lengths every time.
Angles and its Types
Angles are formed by two rays that have the same endpoint or starting point. It can be better understood by looking at the movement of clock-hands. When a clock hand moves, it forms an angle. To measure the 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 measures more than a right angle but less than a straight angle, it is called an obtuse angle.
- Reflex angle: When an angle measures 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. | |
| Acute angled triangle | All the angles are acute. | |
| Right-angled triangle | Anyone angle is the right angle | |
| Based on its angles | Obtuse angled triangle | Anyone angle is obtuse. |
Polygons
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 the 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 |
Quadrilaterals
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 a 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.
Measuring Line Segments
The distance between the endpoints of a line segment is called its length.
Line segments can be measured by
- Comparison by observation
- Comparison by tracing
- Comparison using ruler and divider
Perpendicular Lines
Perpendicular Lines and Perpendicular Bisector
- When two lines intersect and the angle between them is a right angle, then the lines are said to be perpendicular.
- A perpendicular to a line segment that divides it exactly at the midpoint is called the perpendicular bisector.
Classification of Triangles
- Triangles are those closed figures which have exactly three sides.
- Based on their sides and angles, they can be classified into different triangles.
Types of Triangles based on lengths of sides
Based upon the length of the sides, triangles are classified as:
- Scalene
- Isosceles
- Equilateral
Types of Triangles based on angles
Based upon the measure of the angles, triangles are classified as:
- Acute-angled
- Obtuse-angled
- Right-angled
Quadrilaterals
A quadrilateral is a polygon which has four sides.
Comparisons between different Quadrilaterals
Different quadrilaterals can be classified based on the lengths of the sides and angles.
Rhombus
- A rhombus is a special type of parallelogram where all its sides are equal.
- The diagonals are perpendicular to each other. They also bisect the angles.
Trapezium
- A trapezium is a quadrilateral where only two sides are parallel to each other.
- No sides, angles and diagonals are congruent.
Polygons
- A polygon is a closed figure made up of line segments in two-dimension.
- Polygons are classified based on the number of sides.
Rectangle
- A rectangle is a quadrilateral which has opposite sides equal and all angles are right angles.
- The diagonals are equal.
Square
- A square is a quadrilateral which has all sides equal and all angles are right angles.
- The diagonals are equal and perpendicular to each other.
Three Dimensional Shapes
- Three-dimensional shapes are those shapes that can be projected on paper but not drawn on paper.
- These shapes are also called solids.
Faces, Edges and Vertices
- Each side of a three dimensional solid is called the face.
- Two faces meet at a line segment called an edge.
- Three edges meet at a point called a vertex.
Special 3D shapes
- Solids such as the prism and pyramid are considered as special 3D shapes since their structure is very unique.
- A prism with a triangular base is called a triangular prism.
Angles
The amount of rotation about the point of intersection of two planes (or lines) is called angle.
Right, Straight and Complete Angles
- Right angle is equal to 90°.
- Straight angle is equal to 18°.
- Complete angle is one complete revolution or equal to 36°.
Acute, Obtuse and Reflex Angles
- Acute angle is lesser than 90 degree.
- Obtuse angle is greater than 90 degree.
- Reflex angle is greater than 90 degree.
Tools of Construction
- Ruler and divider are used to measure lengths of line segments.
- A protractor is used to measure angles.
Measuring Angles
- Angles are measured in degrees.
- Angles are measured by using a protractor.
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- Separation of Substances: Class 6 Chapter 5 Science Notes
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- Knowing our Numbers: Class 6 Chapter 1 Maths Notes
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- Playing with Numbers: Class 6 Chapter 3 Maths Notes
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