
Mike D. answered 09/25/20
Effective, patient, empathic, math and science tutor
Well suppose Alan gets an x metre head start.
Top speeds are 400/82 m/s for Alan, and 400/76 m/s for Bill.
Assuming they finish at the same time
Bill takes 76s to run the 400 m.
Alan runs (400-x) m, at a speed of 400/82 m/s, taking 76 s
So distance = speed x time, so (400-x) = 76 x 400/82 giving x = 29.3 m