A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is;

Speed = Distance / Time

First, convert the length of the train from meters to kilometers by dividing by 1000 (since 1 kilometer = 1000 meters):

Length of train = 125 m = 125 / 1000 km = 0.125 km

Now, you know that the train passes a man in 10 seconds while the man is running at 5 km/hr in the same direction as the train.

Relative speed of the train with respect to the man = Speed of train - Speed of man Relative speed = Speed of train - 5 km/hr

Since the train is passing the man in the same direction, you can set up the equation:

0.125 km / 10 seconds = (Speed of train - 5 km/hr) / 1 hour

First, calculate the speed of the train in km/hr:

0.125 km / 10 seconds = (Speed of train - 5 km/hr) / 1/3600 hour

Now, simplify the equation:

0.0125 km/s = (Speed of train - 5 km/hr) / (1/3600)

To isolate the speed of the train, multiply both sides by (1/3600):

Speed of train - 5 km/hr = 0.0125 km/s * 3600

Speed of train - 5 km/hr = 45 km/hr

Now, add 5 km/hr to both sides to find the speed of the train:

Speed of train = 45 km/hr + 5 km/hr = 50 km/hr

So, the speed of the train is 50 km/hr.