Page 108 - Revised Maths Wisdom Class - 6

106 MATHS

Perimeter of a Rectangle

A rectangle has four sides with opposite sides equal in length and all its angles are right angles.
D C
Perimeter of rectangle ABCD = AB + BC + CD + DA [AB = CD and DA = BC]

= AB + BC + AB + BC b
= 2(AB + BC)
A l B
= 2(l + b) where ‘l’ is the length and ‘b’ is the breadth of the rectangle.
Perimeter
Length = – breadth
2
Perimeter
Breadth = – Length
2
Perimeter of Triangle

(i) Scalene Triangle
A scalene triangle is a triangle in which all three sides are of different lengths. A
Consider a triangle having three given sides of lengths 5 cm, 7 cm and 8 cm. Find its perimeter.

Perimeter of the triangle ABC = AB + BC + CA 5 cm 7 cm
Perimeter of the triangle = 5 cm + 8 cm + 7 cm = 20 cm.
P B
(ii) Isosceles Triangle 8 cm C
An isosceles triangle is a triangle that has two sides of equal length
6 cm 6 cm
Consider an isosceles triangle having three given sides of lengths 6 cm,
6 cm and 5 cm. Find its perimeter.
Perimeter of the triangle PQR = PQ + PR + QR Q 5 cm R

Perimeter of the triangle = 6 cm + 6 cm + 5 cm = 17 cm.
Note: Perimeter of a triangle = sum of the lengths of its three sides.

Perimeter of Regular Shape

Perimeter of a Square
Perimeter of a square will be the sum of its all sides. As a square has all four sides equal and its all angles are
right angles. P a S
The perimeter of the square PQRS = PQ + QR + RS + SP
= a + a + a + a = 4a
Thus, perimeter of a square = 4 × length of each side a a

Perimeter of Square
And, one side of square =
4 Q a R
Perimeter of an Equilateral Triangle
An equilateral triangle has all its sides equal. The sum of lengths of all the sides is its perimeter.
Let ‘s’ be the side of triangle ABC

Perimeter of DABC = AB + BC + CA