**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.

**(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-**

**(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-**

**(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.

**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-**

**(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**