$A$ man can row $30 \text{ km}$ downstream and return in a total of $8 \text{ h}$. If the speed of the boat in still water is $4$ times the speed of the current,then the speed of the current is ....... $\text{km/h}$.

$A$ man takes $3$ $hours$ $45$ $minutes$ to row a boat $15 \; km$ downstream of a river and $2$ $hours$ $30$ $minutes$ to cover a distance of $5 \; km$ upstream. Find the speed of the river current in $km/hr$.

$A$ person takes total $5$ $hours$ to go to a destination downstream and come back upstream by boat. If the speed of the boat in still water is $10 \text{ km/h}$ and the speed of the stream is $4 \text{ km/h}$,what is the distance of the destination from the starting point (in $\text{km}$)?

$A$ 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 swim at the rate of $4\, km/h$ in still water. If the speed of the water is $2\, km/h$,then the time taken by him to swim $10\, km$ upstream is.........$h$.

$A$ boat goes $20 \text{ km}$ downstream in $1 \text{ h}$ and the same distance upstream in $2 \text{ h}$. The speed of the boat in still water is ......... $\text{km/h}$.