Question

Two trains of 400 m and 475 m in length runs at the speed of 45 km/hr and 'X' km/hr respectively
in opposite directions on parallel tracks. The time taken by them to cross each other is 42
seconds, then find 'X'.​

Answer 1

Answer:

length of two trains = 400 & 475 m

Total length = 400+475 = 875 m

speed of both trains =45 & X km/hr =12.5 & 5X/18 m/s

As they are opposite in direction then, their speed will be added i.e 12.5 + 5X/18 = (225 + 5X)/18 m/s

time taken to cross each other completly = 42 sec

now, we know

speed = total distance/total time

or, (225 + 5X)/18 = 875/ 42

solving it you will get

X = 30 km/ hr

hence the speed of another train = 30 km/hr