How do I find the perimeter of a circle?

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justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

The perimeter or circumference of a circle is given by the formula: Circumference = 2*pi*r , where r is the radius of the circle and pi is a constant.

If you know the radius of the circle, just substitute r in the formula given and you have the circumference or perimeter of the circle.

The perimeter of a circle with radius r is given by 2*pi*r.

bhalachandra's profile pic

bhalachandra | College Teacher | (Level 1) eNoter

Posted on

The  perimeter of a  circle  with  radius r  is  given 

 by  Pi *r*r                                  ...(1)

The  problem  is  that  the  exact  value  of  Pi  is  unknown  and  hence  it  is  impossible  to  determine  the  value  of  the perimeter.

However, if  you  agree  to  approximate  the  value  of  pi  (usually  taken  as  22/7  OR  3.14159),  the   approximate  value  of  the  perimeter  may  be  calculated  by using (1).

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