Question

If the radius of a circle is increased by 75% then its circumference will increase by?

Answer 1

75 %....
circumference= 2pi r

Answer 2

Let the original radius of the circle be - R 
Then the new radius will be                - R + R X 75 / 100
                                                            = 7R/4

The original circumference will be  - 2\pi R 
and new circumference will be       - 2\pi 7R/4 = 11R

Let the increase % in circumference be "c" then 
2\pi R + 2\pi R X c/100 = 11 R
on solving we get 
c= 1.75
hence the circumference will increase by 1.75%