A man travelled a certain distance by train at the rate of 25 kmph. and walked back at the rate of 4 kmph. If the whole journey took 5 hours 48 minutes, the distance was:

20 km
Let the distance be x km.
Total time = 5 hours 48 minutes
$latex = 5+\frac{48}{60} = \left ( 5+\frac{4}{5} \right )hours&s=1$
$latex = \frac{29}{5}hours&s=1$
$latex \therefore \frac{x}{25}+\frac{x}{4} = \frac{29}{5}&s=1$
$latex => \frac{4x+25x}{100} = \frac{29}{5}&s=1$
$latex => 5\times 29x = 29\times 100$
$latex => x = \frac{29\times 100}{5\times 29} = 20km.&s=1$
Hence option [B] is the right answer.