The speed of a boat in still water is $4 \, km/h$ and the speed of the current is $2 \, km/h$. If the time taken to reach a certain distance upstream is $9 \, hours$,find the time it will take to go the same distance downstream (in $hrs$).

Twice the speed downstream is equal to thrice the speed upstream. The ratio of the speed in still water to the speed of the current is:

$A$ 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..........$km/h$.

There is a road beside a river. Two friends started from a place $A,$ moved to a temple situated at another place $B$ and then returned to $A$ again. One of them moves on a cycle at a speed of $12\, km/hr,$ while the other sails on a boat at a speed of $10\, km/hr.$ If the river flows at the speed of $4\, km/hr,$ which of the two friends will return to place $A$ first?

$A$ 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 ....... $\text{km/h}$.

$A$ person can row a certain distance downstream in $6$ $hours$ and return the same distance in $9$ $hours.$ If the stream flows at the rate of $2 \frac{1}{4} \text{ km/h},$ find how far he can row in an hour in still water (in $\text{km/h}$).