The ratio of the outer and the inner circumference of a circula path is 17 : 15. In the path is 40 metres wide, then what is the radius of the inner circle?

300m

The width of the path = Outer radius(R) - Inner radius(r)

Ratio of outer(R) and inner(r) circumference = 2$\pi$R  :  2$\pi$r = 17 : 15

⇒ R  :  r = 17  :  15

⇒ difference in the ratios = R - r = 2x

we know. that R - r = 40(width of the path)

                   ⇒ 2x  = 40    

                   ⇒  x  = 20

Radius of inner circle(r) = 15 x 20 = 300m