A train of length 180 meters crosses a man running at 10 km/hr in the same direction in 10 seconds. What is the speed of the train?

Question: A train of length 180 meters crosses a man running at 10 km/hr in the same direction in 10 seconds. What is the speed of the train?

Solution:
When the train and man are moving in same direction then relative speed will be the difference between their individual speeds. In this problem the other way to find the relative speed is to divide the distance covered (length of train) by the time taken by the train to cross the man.

Relative Speed = 180/10 m/s

We will convert it into Km/hr
(180/10) × (18/5) = 64.8 km/hr

Now, let the speed of the train is X km/hr.
So, the relative speed, 64.8 km/hr = X km/hr - 10 km/hr
⇒ X - 10 = 64.8
⇒ X = 64.8 + 10
∴ X = 74.8 km/hr