This problem is to calculate the difference between the inner and outer circular runways, select the same point as the benchmark, and set the radius as r, then the radius of the inner runway is R+ 1.2, and the radius of the outer runway is r+2.4;

Distance of inner semi-circular runway l1= [2 (r+1.2) * 3.14]/2 Distance of outer semi-circular runway L2=[2(R+2.4)*3. 14]/2.

L2-L1= (r+2.4) * 3.14-(r+1.2) * 3.14 = 3.768 is rounded to 3.8.

The starting point of the outer runway should be moved forward 3.8m.