Math > Year 3

Introducing perimeter

What is Perimeter?
Perimeter is the distance around a 2D shape.
To work out the perimeter, add up the lengths of all the sides.


Perimeter of Triangle

To find the perimeter of the given triangle, we’ll add the lengths of all the sides.

 

Perimeter = 3cm + 3cm + 3cm = 9cm

 

Perimeter of rectangle

 

To find the perimeter of the given rectangle, we’ll add the lengths of all the sides.

Perimeter = 3cm + 3cm + 2cm + 2cm = 10cm
 


Perimeter of Square

 

To find the perimeter of the given square, we’ll add the lengths of all the sides.

Perimeter = 4cm + 4cm + 4cm + 4cm = 16 cm

 


If the length of all the sides of a shape is the same, we can find the perimeter by multiplying the number of sides by the length.

 

Let us try a question.
 


 

To find the perimeter of the given pentagon, we’ll add the lengths of all the sides.

 Perimeter = 7 cm + 7 cm + 7cm +7 cm + 7cm = 35cm

So, the perimeter of the given figure is 35cm.


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