A train left point A at 12 noon. Two hours later, another train started from point A in the same direction. It overtook the first train at 8 PM. It is known that the sum of the speeds of the two trains is 140 km/hr. Then, at what time would the second train overtake the first train, if instead the second train had started from point A in the same direction 5 hours after the first train? Assume that both the trains travel at constant speeds.

When the second train starts two hours late and overtakes the first train at 8 PM, it has travelled for 6 hours while the first train has travelled for 8 hours. Equating their distances gives 6 times the second train's speed equal to 8 times the first train's speed, making their speed ratio 4:3. Since the sum of their speeds is 140 kmph, their speeds are 80 kmph and 60 kmph, respectively. If the second train starts 5 hours after the first train, the first train has a head start of 300 kilometers (60 kmph multiplied by 5 hours). The relative speed is 80 kmph minus 60 kmph, which equals 20 kmph, meaning it will take the second train 300 divided by 20, or 15 hours, to catch up. Starting at 5 PM, adding 15 hours results in an overtaking time of 8 AM the next day.

• Thanks
• Wrong explanation