# Mensuration| Perimeter| Area| Surface Area| Volume

Notes of chapter: Mensuration| Perimeter| Area| Surface area| Volume are presented below. Indepth notes along with worksheets and NCERT Solutions.

(1) Total length of outline of a closed figure is known as perimeter of that figure.

(i) Perimeter of polygons-

(a) Perimeter of any equilateral polygon is multiplication of sides with number of sides.

Perimeter of an equilateral polygon = n × side

Where, n = number of sides of equilateral polygon

Therefore perimeter of square, rhombus, equilateral triangle, equilateral pentagon or any other equilateral polygon can be calculated by above formula.

Polygon

Square

(A)Perimeter of a square = n × side

Where, n = number of sides of square

Perimeter of a square = 4 × side

Eg:- Find the perimeter of square ABCD whose one side is 3 cm.

Ans-

(B) Perimeter of a rhombus = n × side

Where, n = number of sides of rhombus

Perimeter of a rhombus = 4 × side

Eg:- Find the perimeter of rhombus ABCD whose one side is 3 cm.

Ans-

Rhombus

(C) Perimeter of an equilateral triangle = n × side

Where, n = number of sides of an equilateral triangle

Perimeter of an equilateral triangle = 3 × side

Eg:- Find the perimeter of equilateral triangle ABC whose one side is 3 cm.

Ans-

Equilateral triangle

(D) Perimeter of an equilateral pentagon = n × side

Where, n = number of sides of an equilateral pentagon

Perimeter of an equilateral pentagon = 5 × side

Eg:- Find the perimeter of equilateral pentagon ABCDE whose one side is 3 cm.

Ans-

(b) Perimeter of general polygons

Perimeter of general polygons can be calculated by adding lengths of the all sides of the general polygon.

Perimeter of general polygon = sum of the all sides of general polygon

Therefore, perimeter of parallelogram, rectangle, trapezium or any other shape can be calculated by adding all sides of that shape.

(A)Perimeter of parallelogram = sum of all sides

Eg:- Find the perimeter of parallelogram ABCD whose one side(AB) is 3 cm and other side (BC) is 2 cm.

Ans-

(B) Perimeter of a rectangle = 2 × (l + b)

Where,

l = length of the rectangle

b = breadth of the rectangle

Eg:- Find the perimeter of rectangle ABCD whose one side(AB) is 3 cm and other side (BC) is 2 cm.

Rectangle

Ans-

(C)Perimeter of triangle = sum of all sides

Eg:- Find the perimeter of triangle ABC whose sides are 7 cm, 4 cm and 10 cm.

Ans-

Circle

Parallelogram

(iv) Surface area of a right circular cone

A right circular cone is a hollow cone in which surface area is generated by a perpendicular line which is passes through center of the circular base.

The cone is made up of small triangles as shown in figure below-

Helping Topics

NCERT Solution Class 7

NCERT Solutions Class 8

NCERT Solution Class 9

Worksheet Class 7

Worksheet Class 8

Worksheet Class 9