CIRCUMFERENCE OF A CIRCLE

Another term of Perimeter of a circle is known as circumference of a circle. This page is going to guide you how to find the perimeter of a circle. 

Formula :

Circumference of circle = 2 Π r

Here the value of Π is either 22/7 or 3.14 and "r" stands for radius of a circle.

Here the length of the red line is known as circumference of a circle. Now let us see some example problems to understand this topic better.

Example 1:

Find the circumference of a circle whose radius is 14 cm.

Solution:

To find the circumference of circle we need to use the formula to find the circumference of circle.

Circumference of circle   =  2 Πr

  =  2 ⋅ (22/7) ⋅ 14

  =  2 ⋅ 22 ⋅ 2

  =  4 ⋅ 22

  =  8 cm

Example 2:

Find the diameter of circle whose circumference is 42 cm.

Solution:

Circumference of circle = 42 cm

2 Π r  =  42

2 ⋅ (22/7) ⋅ r  =  42

r  =  (42 ⋅ 7) / (2 ⋅ 22)

r  =  294/44

r  =  6.68 cm

Now we have to find the diameter for that we have to multiply the radius by 2.

Diameter   =  2 r

=  2(6.68)

= 13.36 cm

Example 3:

A moon is about 384000 km away from the earth and its path around the earth is nearly circular. Find the distance traveled by moon every month.

Solution :

In one month, the moon describes a full circle about the earth.

Now the circumference  =  2 Π r

=  2 ⋅ (22/7) ⋅ 384000 km

=  2413714 km

Hence the distance traveled by the moon  =  2413714 km

Example 4 :

A copper wire is in the form of a circle with radius 35 cm. It is bent into a square. Determine the side of the square.

Solution :

Given: Radius of a circle, r = 35 cm.

Since the same wire is bent into the form of a square,

Perimeter of the circle  =  Perimeter of the square

Perimeter of the circle  =  2Πr units

=  2 ⋅ (22/7) ⋅ 35

P  =  220 cm

Let ‘a’ be the side of a square.

Perimeter of a square = 4a units

4a  =  220

a  =  55 cm

Side of the square = 55 cm.

After having gone through the stuff above, we hope that the students would have understood circumference of a circle. 

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