A train X travelling at 60 km/h overtakes another train Y, 225 m long, and completely passes it in 72 seconds. If the trains had been going in opposite directions, they would have passed each other in 18 seconds. The length (in m) of X and the speed (in km/h) of Y are, respectively:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e 255 and 36
| Understanding | Application |
| The time is taken by train to overtake a train running parallel is the ratio of the sum of both trains to the relative speed. |
Let the length of train X m be L and the speed of train Y be V km/h When both are travelling in the same direction. ⇒ 72 = (225 + L) / (50 / 3 - V) ⇒ L + 72V = 975 When both are travelling in the opposite direction. ⇒ 18 = (225 + L) / (50 / 3 + V) ⇒ L = 75 + 18V By solving both the equations ⇒ v = 10 m/s ⇒ 10 × (18 / 5) ⇒ 36 km/h L = 75 + 18(10) ⇒ 255 m |