Boats and Streams question bank (Quantitative Aptitude)

$A$ man can row against the current $3/4$ of a kilometre in $15$ $min$ and returns the same distance in $10$ $min.$ The ratio of his speed to that of the current is:

$A$ steamer goes downstream from one port to another in $4\, h$. It covers the same distance upstream in $5\, h$. If the speed of the stream is $2\, km/h$,then find the distance between the two ports (in $km$).