4th Class Mathematics Area, Perimeter and Volume Area and Perimetre

 Area and Perimetre

Introduction

In the previous chapter we have studied about the shape and size of some geometrical figures. In this chapter we will study about area and perimetre of some close geometrical figures,

Area

Area is referred as the surface occupied by the geometrical shapes

Area of a Triangle

Area of a triangle

Where base is one side of a triangle and height is the length of altitude drawn from opposite vertex on the given base,

Area of the triangle

Where BC is the base and AD is the height,

•            Example

Find the area of the triangle whose base is 5 cm and height is 8 cm.

Solution:

Area of the triangle

Area of a Rectangle

Area of a rectangle

Area of the rectangle

•            Example

Find the area of the rectangle whose length is 9 cm and width is 7 cm,

Solution:

Area of the rectangle = 9 cm x 7 cm = 63 cm2

Area of a Square

Area of a square

Area of the square

•            Example

Find the area of the square whose length of one side is 6 cm.

Solution:

Area of the square

Area of a circle

Area of the circle

Where

•              Example

Find the area of the circle whose radius is 0.7 cm.

Solution:

Area of the circle

Perimetre

Perimetre is referred as the length of the boundary line which endorse the

Perimetre of the Triangles

Perimetre of a triangle = Sum of length of all three sides.

Perimetre of the triangle

•             Example

Find the perimetre of the given figure.

Solution:

Perimetre of the figure

Perimetre of a Quadrilateral

The perimetre of a quadrilateral = Sum of the length of all four sides.

Perimetre of the quadrilateral

•             Example

Find the perimetre of the quadrilateral whose lengths are  and 5.2cm.

Solution:

Perimetre of the quadrilateral

Perimetre of a Rectangle

Perimetre of a rectangle

Perimetre of the rectangle

•            Example

Find the perimetre of the rectangle whose length and breadth are 9 cm and 8 cm.

Solution:

Perimetre of the rectangle

Perimetre of a Square

Perimetre of a square = 4  length of one side of the square.

Perimetre of the square

•            Example

Find the perimetre of the square whose length of one side is 4.25 cm.

Solution:

Perimetre of the square

Perimetre of a circle

Perimetre of a circle

Or Perimetre of a circle

Where

Or Perimetre of the circle

•             Example

Find the perimetre of the circle whose radius is 10 cm.

Solution:

Perimetre the circle