Area and Volume

Let
the radius of the outer circular racing track is R
the radius of the inner circular racing track is r

Then the circumference of the outer circular racing track is 2πR
the circumference of the outer circular racing track is 2πr

We know that
2πR-2πr=60

2π(R-r)=60

R-r=60/2π=9.5493

So the width of the trunk is 9.5493 m

let x m be the radius of the inner racing track and y m be the width of the track

2π(x+y) - 2πx = 60
2πx + 2πy - 2πx = 60
2πy = 60
y=60/π

2008-05-18 17:09:19 補充：
2πy = 60
y=30/π