Two trains moving in the same direction, and running respectively at 36km/h and 72km/h cross each other in 7sec. What is the length of each train if the two trains are equally long?
The trains cover a distance equal to the sum of their lengths at a relative speed 72 - 36 = 36km/h × (5/18), or 10m/s. We can use the speed distance formula: sum of lengths = 10 × 7 = 70m. Halving this we get the length of one train = 35m.