A man travelled a certain distance by train at the speed of 50 km/hr and walked back the same distance at the speed of 10 km/hr. If the whole journey took 12 hours, then what was the distance travelled by train?

100 km

Let the distance covered by train or by walking = D km

Total Time = 12 hours

Time taken by train + Time train by Walking = 12

\(\frac{D}{50}\) + \(\frac{D}{10}\) = 12

\(\frac{6D}{50}\) = 12

D = 100

So , Total distance =  100 km