# Find the value of X

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

- 28 km/hr
- 30 m/s
- 32 m/s
- 30 km/hr

**Answer: (2) 30 m/s**

**Explanation:-
**According to the question,

(400 + 475)/(45 + X) x 5/18 = 42

875 x 18/5 (45 + X) = 42

175 x 18 /42 = 45 + X

75 = 45 + X

X = 75 – 45

X = 30 m/s

Then, the speed of the train X is 30 m/s.

Hence, the answer is (2) 30 m/s.