Check sibling questions

Let us take a circle

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Distance around the circle is called circumference of circle.

So, Perimeter of circle is actually circumference of circle.

 

For a circle with radius r,

  Circumference = 2πœ‹r

Here,

     r is the radius,

and

     πœ‹ = pi

It’s value is

        πœ‹ = 3.14159265359……

 

We write it as

        πœ‹ = 3.14 or πœ‹ = 22/7

 

Let’s take some examples

 

Find circumference of circle with radius 3.5 cm

Circumference of circle - Part 2

 

Radius = r

            = 3.5 cm

Circumference = 2πœ‹r

 = 2 × 22/7 × 3.5

 = 2 × 22/7 × 35/10

 = 2 × 22/1 × 5/10

 = 22 × 5/5

 = 22 × 1 = 22 cm

 

Find circumference of circle with radius 7.0 cm

Circumference of circle - Part 3

Radius = r

            = 7 cm

 

Circumference = 2πœ‹r

 = 2 × 22/7 × 7

 = 2 × 22/1 × 1

 = 44 cm

 

Find circumference of circle with diameter 21 cm

Circumference of circle - Part 4

Diameter = 21 cm

Radius = r = Diameter/2

    = 21/2

 

Circumference = 2πœ‹r

 = 2 × 22/7 × 21/2

 = 22/7 × 21/1

 = 22 × 3

 = 66 cm

 

Find circumference of circle with diameter 42 cm

Circumference of circle - Part 5

Diameter = 42 cm

   Radius = r = Diameter/2

= 42/2

= 21 cm

 

Circumference = 2πœ‹r

 = 2 × 22/7 × 21

 = 2 × 22/1 × 3

 = 44 × 3

 = 132 cm

 

Find circumference of circle with radius 5 cm

Circumference of circle - Part 6

Radius = r

            = 5 cm

 

Circumference = 2πœ‹r

 = 2 × 3.14 × 5

 = 3.14 × 5 × 2

 = 3.14 × 10

 = 31.4 cm

 

Find circumference of circle with diameter 30 cm

Circumference of circle - Part 7

Diameter = 30 cm

Radius = r = Diameter/2

  = 30/2

  = 15 cm

Circumference = 2πœ‹r

 = 2 × 3.14 × 15

 = 3.14 × 2 × 15

 = 314/100 × 30

 = 314/10 × 3

 = 942/10

 = 94.2 cm

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.