Hey could someone help me solve this question? Two trains travelling at speeds of 36 kmph and 54 kmph cross each other in 8 seconds when travellling in opposite directions. Had they been travelling in same direction, in how much time would the faster train have crossed the slower train?

Speed of first train = 36 km/h = 10 m/s Speed of second train = 54 km/h = 15 m/s Time to cross in opposite directions = 8 seconds Relative speed (opposite directions): 10 + 15 = 25   m/s 10+15=25m/s Total length of both trains: 25 × 8 = 200   m 25×8=200m Relative speed (same direction): 15 − 10 = 5   m/s 15−10=5m/s Time to cross in same direction: 200 5 = 40   seconds 5 200 ​ =40seconds

First convert 36 and 54 into m/s by multiplying by 5/18 U get 10m/s and 15m/s. Now as speed equals distance/time u have total speed when traveling in same direction as 15+10 and time as 8 u get distance 8*25 equals 200. This is the length of the two trains now in the same direction the speeds will be subtracted 15-10 i.e. 5 m/s relative speed so 200/5 equals 40 secs this is your answer hope this helps