A train crosses two persons travelling at 4 km/h and 6 km/h in the same direction in 12 sec and 14 sec, respectively. The speed of the train is ________.

18 km/h

Let speed of train = x km/h

According to question ,

( x - 4 ) × \(\frac{12}{3600}\) = ( x - 6 ) × \(\frac{14}{3600}\)

( x - 4 ) × \(\frac{1}{300}\) = ( x - 6 ) × \(\frac{7}{1800}\)

( x - 4 )  = ( x - 6 ) × \(\frac{7}{6}\)

6x - 24 = 7x - 42

x = 42 - 24 = 18 km/h

So , speed of train is 18 km/h.