Two trains leave New Delhi at the same time. One travels north at 60 kmph and the other travels south at 40 kmph. After how many hours will the trains be 150 km apart ?

When two objects move in opposite directions, their relative speed is the sum of their individual speeds. Here relative speed = 60 km/h + 40 km/h = 100 km/h . Using the basic relation Time = Distance / Speed, the time taken for them to be 150 km apart is 150 km ÷ 100 km/h = 1.5 hours, which equals 3/2 hours. The calculation directly applies the standard speed–distance–time formula and the rule for relative speed in opposite motion . The same problem statement appears in available practice sources illustrating this standard approach .