# Class 6 Maths Chapter 5 Exercise 5.5 Pdf Notes NCERT Solutions

Class 6 Maths Chapter 5 Understanding Elementary Shapes Exercise 5.5 pdf notes:-

Exercise 5.5 Class 6 maths Chapter 5 Pdf Notes:-

## Ncert Solution for Class 6 Maths Chapter 5 Understanding Elementary Shapes Exercise 5.5 Tips:-

Perpendicular Lines
When two lines intersect and the angle between them is a right angle, then the
lines are said to be perpendicular. If a line AB is perpendicular to CD, we
write AB ⊥ CD .
Think, discuss and write
If AB ⊥ CD , then should we say that CD ⊥ ABalso?
Perpendiculars around us!
You can give plenty of examples from things around you for perpendicular
lines (or line segments). The English alphabet T is one. Is there any other
alphabet which illustrates perpendicularity?
Consider the edges of a post card. Are the edges
perpendicular?
Let AB be a line segment. Mark its mid point
as M. Let MN be a line perpendicular to AB
through M.
Does MN divide AB into two equal parts?
MN bisects AB (that is, divides AB into two
equal parts) and is also perpendicular to AB.
So we say MN is the perpendicular bisector of AB.
You will learn to construct it later.

What have we discussed?

1. The distance between the end points of a line segment is its length.
2. A graduated ruler and the divider are useful to compare lengths of line
segments.
3. When a hand of a clock moves from one position to another position we have
an example for an angle.
One full turn of the hand is 1 revolution.
A right angle is 1⁄4 revolution and a straight angle is 1⁄2 a revolution .
We use a protractor to measure the size of an angle in degrees.
The measure of a right angle is 90° and hence that of a straight angle is 180°.
An angle is acute if its measure is smaller than that of a right angle and is obtuse
if its measure is greater than that of a right angle and less than a straight angle.
A reflex angle is larger than a straight angle.
1. Two intersecting lines are perpendicular if the angle between them is 90°.
2. The perpendicular bisector of a line segment is a perpendicular to the line
segment that divides it into two equal parts.
1. Triangles can be classified as follows based on their angles:
Nature of angles in the triangle Name
Each angle is acute Acute angled triangle
One angle is a right angle Right angled triangle
One angle is obtuse Obtuse angled triangle
2. Triangles can be classified as follows based on the lengths of their sides:
Nature of sides in the triangle Name
All the three sides are of unequal length Scalene triangle
Any two of the sides are of equal length Isosceles triangle
All the three sides are of equal length Equilateral triangle
3. Polygons are named based on their sides.

Number of sides Name of the Polygon
3 Triangle
5 Pentagon
6 Hexagon
8 Octagon

1. Quadrilaterals are further classified with reference to their properties.
One pair of parallel sides Trapezium
Two pairs of parallel sides Parallelogram
Parallelogram with 4 right angles Rectangle
Parallelogram with 4 sides of equal length Rhombus
A rhombus with 4 right angles Square
2. We see around us many three dimensional shapes. Cubes, cuboids, spheres,
cylinders, cones, prisms and pyramids are some of them.

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