Correct Option (C)
To determine the distance from Delhi where the express train meets the freight train, the following steps are applied:
- The freight train travels for 2 hours before the express train commences its journey. During this period, the freight train covers a distance of 40 km/hr × 2 hr = 80 km. This establishes the initial separation between the two trains when the express train starts.
- The relative speed at which the express train closes this gap is the difference between their speeds: 60 km/hr - 40 km/hr = 20 km/hr.
- The time required for the express train to cover the initial 80 km separation at a relative speed of 20 km/hr is calculated as: Time = Distance / Relative Speed = 80 km / 20 km/hr = 4 hours.
- Therefore, the express train travels for 4 hours to meet the freight train. The distance from Delhi where they meet is the distance covered by the express train in this time: Distance = Speed × Time = 60 km/hr × 4 hr = 240 km.
Incorrect Options:
Options (A) 480 km, (B) 260 km, and (D) 120 km are incorrect. These values do not correspond to the distance calculated by applying the principles of relative speed and time to the given problem parameters.