RRB Group D 1-Dec-2013 Shift 1 Solved Paper

A will have to cover a distance of(500 – 140) m, i.e., 360 m.
While A covers 3 m, B covers 4 m.
While A covers 360 m, B covers 4/3 × 360 = 480 m.
Thus, when A reaches the winning post, B covers 480 m and therefore, remains 20 m behind A.