Train A running at 81 km/h takes 72 sec to overtake

Solution

Given- speed of A = 81km/h, distance of B = 600m Let speed of B = B, and distance of A = x  When both the trains are running in the same direction  (A – B) × 72 = x + 600 5/18 (81 – B) × 72 = x + 600 ... (1) When both the trains are running in the opposite direction  5/18 (81 + B) × 36 = x + 600 ... (2) From (1) and (2) 5/18 × (81 – B)72 = (81 + B) 36 ×5/18  81 × 2 – 2B = 81 + B 3B = 81  B = 27  Put the value of B in (1)  (81 – 27) × 72 × 5/18 = x + 600  1080 – 600 = x  x= 480 m