The time taken by a train 360 m long travelling at 21 kmph, in passing a person walking in the same direction at 3 kmph, will be:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 72 Sec
When the train and the person move in the same direction, the train gains on the person only by the difference of their speeds (the relative speed). To pass the person, the train must cover its own length at this relative speed.
Relative speed \(=21-3=18\) km/h
\(\displaystyle 18\text{ km/h}=18\times\frac{5}{18}=5\) m/s
\(\displaystyle \text{Time}=\frac{360}{5}=\) 72 seconds