A train of length 120 m travelling with a speed of 40 m/s catches another train of length 80 m travelling in the same direction and then leaves it 100 meters behind in 20 seconds. The speed of the second train is:
Solution
Correct Answer: Option E
Let the speed of the second train be y m/s
∵ both the trains are moving in the same direction, So relative speed of first train with respect to other = speed of first train – speed of second train = (40 – y) m/s
When the first train crosses the second train, it covers a distance equal to the sum of lengths of both the trains.
But in this case, the first train not only crosses the secon train, but also leaves it behind by 100m
∴ Distance covered by 1st train = (length of 1st train + length of 2nd train + 100) m
⇒ Distance covered by 1st train = 120 + 80 + 100 = 300 m
Time = 20 seconds
We know that, Speed = distance/time
⇒ (40 – y) = 300/20
⇒ 40 – y = 15
⇒ y = 25 m/s
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