80m and 120m long two trains are running in same direction on a parallel track at the speed of 25 km/hr and 35 km/hr respectively. In how many seconds will they cross each other ?

When trains move in the same direction, subtract their speeds to get relative speed. Relative speed = 35 - 25 = 10 km/hr, which converts to 25/9 m/s. Total crossing distance is sum of train lengths: 80 + 120 = 200 m. Time = 200 ÷ (25/9) = 72 seconds. Option A (48) would be the answer if trains were moving in opposite directions.