Keshav can row $60 \ km$ downstream and $36 \ km$ upstream,taking $10 \ h$ each time. What is the velocity of the current? (in $km/h$)

$A$ swimmer covers a distance of $28\, km$ against the current and $40\, km$ in the direction of the current. If in each case he takes $4\, hours$,then the speed of the current is..........$km/h$.

$A$ man can row $6\, km/h$ in still water. If the river is running at $2\, km/h$,it takes $3\, hours$ more to row upstream than to row downstream for the same distance. How far is the place? (in $km$)

$A$ man can row three-quarters of a kilometre against the stream in $11 \frac{1}{4}$ minutes. The speed (in $km/hr$) of the man in still water is

$A$ sailor goes $12$ $km$ downstream in $48$ $min$ and returns in $1$ $h$ $20$ $min.$ The speed of the sailor in still water is..........$km/h$.

$A$ boat goes $48\, km$ downstream in $20\, h$. It takes $4\, h$ more to cover the same distance against the stream. What is the speed of the boat in still water? (in $km/h$)