(c) Let the length of the train be L metres and speeds of the train, Arjun and Srikrishna be R, A and K respectively, then
L
R−A
=36..(i) and
L
(R+K)
=24...(ii) From eq. (i) and (ii) 3(R − A)= 2(R + K) ⇒ R = 3A + 2K In 30 minutes (i.e., 1800 seconds), the train covers 1800R (distance) but Arjun also covers 1800A (distance) in the same time. Therefore distance between Arjun and Srikrishna, when the train has just crossed Srikrishna = 1800(R − A)−24 (A + K) ∴ Time required =