### Perimeter (Square, Rectangle, Triangle and Rectilinear figure

**Tags:**Perimeter of square for class IV, Rectangle, Triangle, Scalene triangle, Isosceles, Equilateral triangle, Perimeter of rectilinear figure for class 4, Perimeter formula, Perimeter for grade 4, Perimeter question, Perimeter worksheet PDF, Perimeter quizPerimeter

Let’s start the topic with a small activity.

**Step 1:**Measure all the sides of your table or handkerchief using ruler.**Step 2:**Calculate the sum of the length of all sides.**Step 3:**Write the final calculated measurement. The final answer we got is the total length of the boundary. The length of the boundary is known as__perimeter__.Therefore,

__perimeter means distance around a figure or curve.__We can only measure perimeter of a closed figure/2 dimensional shape or curve as movement around a closed figure or curve is possible.__Example:__We cannot move around the below figure.If we start our journey from point A, we will reach point C but cannot reach back to point A as it is open figure.

Perimeter of a Square

A square is a closed figure that has 4 sides of equal length and 4 equal angles of 90 degree.

Perimeter of a square = sum of all sides

OR 4 x side

__Example__: Side of square 10 cm*Method 1:*Perimeter = 10 + 10 + 10 + 10 (sum of all 4 sides)= 40 cm

*Method 2:*As all sides are equal we can write 4 times side in place of adding all sides.Perimeter = 4 x 10 cm

= 40 cm

Perimeter of a Rectangle

A rectangle is a closed figure that has equal opposite sides and each angle is of 90 degree. The longer side of rectangle is known as

__length__of the rectangle and shorter side is known as__width or breadth__of rectangle.Perimeter of Rectangle = L + L + B + B

OR

2 X L + 2 X B (i.e. 2L + 2B)

OR

2 (L + B) (taking 2 common i.e. twice the sum of length and breadth)

__Example__: Length =10cm and Breadth = 5cm

*Method 1:*Perimeter = 10 + 10 + 5 + 5 (sum of all 4 sides)= 30 cm

*Method 2:*As opposite sides are equal we can write sum 2 times length and 2 times breadth.Perimeter = 2 X L + 2 X B (i.e. 2L + 2B)

= 2 x 10 + 2 x 5

= 20 + 10

= 30 cm

OR

= 2 (L + B)

= 2 (10 + 5) (solve bracket first)

= 2 X 15

= 30 cm

Perimeter of a Triangle

Scalene Triangle - A triangle whose all three sides are of different length and all 3 angle are of different measurement is known as scalene triangle.Perimeter of Triangle = Side 1 + Side 2 + Side 3

__Example:__Perimeter = AB + BC + CA

= 5 cm + 10 cm + 12 cm

= 27 cm

Isosceles Triangle - A triangle whose two sides are of equal length and 2 angle are of equal measurement is known as isosceles triangle.

Perimeter of Triangle = Side 1 + Side 2 + Side 3

__Example:__Perimeter = AB + BC + CA

= 10 cm + 15 cm + 10 cm

= 35 cm

Equilateral Triangle - A triangle whose all sides are of equal length and all angle are of equal measurement is known as equilateral triangle.

Perimeter of Triangle = Side 1 + Side 2 + Side 3

OR

= 3 x length of triangle (as all 3 sides are equal)

__Example:__Perimeter = AB + BC + CA

= 10 cm + 10 cm + 10 cm

= 30 cm

OR

= 3 X 10 cm

= 30 cm

**Note:**Perimeter of any rectilinear figure (figure bounded by straight lines) is the sum of the measurement of all sides.__Example:__

Perimeter of the above figure = AB + BC + CD + DE + EA

= 12 cm + 5 cm + 5 cm + 12 cm + 10 cm

= 44 cm

**Download to practice offline.**