UPSC 2015 CDS I Math Paper

Let the radius of the inner circular path be r m.
Therefore, the radius of the outer circular path =(r+5)m
Perimeter of the outer circular path : Perimeter of the inner circular path = 23 : 22
⇒

2π(r+5)

2πr

=

23

22

⇒

5

r

=

23

22

−1=

1

22

⇒=110m
Therefore, diameter of inner circle =2×110=220m