Question

If the circumference is 30 centimetre more than the diameter of the circle, find the radius of the circle.

Answer 1

circumference= diameter +30 cm
                       = 2r + 30 cm

2 x pi x r= 2r + 30
2 x 22/7 x r = 2r + 30
44r/7 = 2r + 30
44r/7 - 2r = 30
(44r - 14r)/7 = 30
30r/7 = 30
r = (30 x 7) / 30 cm
r= 7 cm

Answer 2

Let the radius of circle r then diameter will be 2r

According to question
Circumference = 30+2r
2πr=30+2r

2*22/7*r=30+2r

44/7*r-2r=30

30r/7=30

r=7 cm