Question

if the circumference of a circle exceed its diameter by 30 cm. find the radius of the circle

Answer 1

Circumference - Diameter = 30

=> 2 * pi *r - 2r = 30

=> 2*r ( pi - 1) = 30

=> 2r (22-7)/7 = 30

=> 2r * 15 = 30 * 7

=> 30r = 210

=> r = 210 / 30

=> r = 7 cm

Radius of circle = 7 cm

Answer 2

Let, diameter of the circle be x

So,
the Circumference will be x+30
the radius of the circle be x/2

Formula for calculating Circumference of a circle = 2πr

Comparing the formula and the value of Circumference...

2πr = x+30
2π(x/2)=x+30
πx= x+30
22x/7=x+30
22x=7x+210
15x=210
x= 14cm

Now, radius of the circle = x/2= 14/2 = 7cm