A train 150 metres long crosses a milestone in 15 seconds and crosses another train of the same length travelling in the opposite direction in 12 seconds. The speed of the second train in km/hr is

It is given that A train 150 meters long crosses a milestone in 15 seconds

Length of train(L) = 150 m

Time taken to cross milestone(T) = 15 sec

Let speed of this train be = S m/sec

So using ,

Distance = Speed x Time

150 = S x 15

S = 10 m/sec

Now it is mentioned that this train crosses another train of the same length travelling in the opposite direction in 12 seconds

let the speed of another train be Y m/sec

As both trains are moving in opposite direction so relative speed = (Y + 10) m/sec

So ,

(150+150) = (Y + 10) x 12

25 = Y + 10

Y = 15 m/sec OR (15 x $$\frac{18}{5}$$ ) = 54 km/hr