The circumstance of a circle is represented by 2 pie r. If the radius of the circle is double, then the circumference is

The circumference of the circle is given by C = 2 π r

If the radius of the circle is doubled, then new radius will be r' = 2r.

And new circumference will be C' = 2·π· (2r) = 2· (2 π r) = 2·C

It is clearly visible that new circumference is twice the original circumference i. e. C' = 4 π r