A man sitting on a train which is traveling at 50 km/hr observes that a goods train, traveling in the opposite direction, takes 9 seconds to pass him. If the goods train is 280 meter long, find its speed?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 62 km/hr
When two trains move in opposite directions, each passes the other at the sum of their speeds (the relative speed). To pass the man, the goods train covers only its own length, 280 m.
Relative speed \(\displaystyle =\frac{280\,\mathrm{m}}{9\,\mathrm{s}}=\frac{280}{9}\,\mathrm{m/s}\)
In km/hr (multiply by \(\frac{18}{5}\)): \(\displaystyle \frac{280}{9}\times\frac{18}{5}=112\) km/hr
Speed of the goods train \(=112-50=62\) km/hr