Let’s take a triangle ABC

15.jpg

Perimeter of ∆ABC = Sum of all sides

= AB + BC + AC

 

What about specific triangles?

 

Perimeter of Isosceles triangle

In an Isosceles triangle,

  Two sides are equal

 

Here,

  AB = AC = a

  BC = b

 

So,

   Perimeter ∆ABC = Sum of all sides

= AB + BC + AC

= a + b + a

= 2a + b

 

Perimeter of Equilateral triangle

In an Equilateral triangle,

  all sides are eqaul

16.jpg

Here,

  AB = AC = BC = a

 

So,

   Perimeter ∆ABC = Sum of all sides

= AB + BC + AC

= a + a + a

= 3a

 

Let’s take some examples

 

Find perimeter of Δ ABC

17.jpg

Perimeter of ∆ABC = Sum of all sides

= AB + BC + CA

= 3 + 5 + 4

= 12 cm

 

∴ Required perimeter is 12 cm

 

Find perimeter of Δ ABC

18.jpg

Perimeter of ∆ABC = AB + BC + CA

= 15 + 24 + 12

= 51 cm

∴ Required perimeter is 51 cm

 

Find perimeter of Δ ABC

19.jpg

Perimeter of ∆ABC = AB + BC + CA

= 15 + 24 + 12

= 51 cm

 

∴ Required perimeter is 51 cm

 

Find perimeter of Δ ABC

20.jpg

Perimeter of ∆ABC = Sum of all sides

        = AB + BC + AC

        = 12 + 17 + 10

        = 39 cm

 

∴ Required perimeter is 39 cm

 

Find perimeter of Δ ABC

21.jpg

Here,

  AB = AC = 8cm

  BC = 4 cm

 

    Perimeter of ∆ABC = Sum of all sides

    = AB + BC + AC

    = 8 + 4 + 8

    = 20 cm

 

∴ Required perimeter is 20 cm

 

Find perimeter of Δ ABC

22.jpg

Since all sides are equal,

it is an equilateral triangle

Here, AB = BC = CA = a = 5cm

 

Perimeter of equilateral ∆ABC = 3a

  = 3 (5)

  = 15 cm

 

∴ Required perimeter is 15 cm

 

Find perimeter of Δ ABC

23.jpg

Since all sides are equal,

it is an equilateral triangle

Here, AB = BC = CA = a = 9 m

 

Perimeter of equilateral ∆ABC = 3a

= 3 (9)

= 27 cm

 

∴ Required perimeter is 27 cm

  1. Chapter 10 Class 6 Mensuration
  2. Concept wise

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.