The speed of a boat in still water is $6\, km/h$. It takes the boat twice as long to row up as to row down the river. Find the rate of the stream (in $km/h$).

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?

$A$ boat covers $24 \text{ km}$ upstream and $36 \text{ km}$ downstream in $6 \text{ hours}$,while it covers $36 \text{ km}$ upstream and $24 \text{ km}$ downstream in $6.5 \text{ hours}$. The velocity of the current is ......... $\text{km/h}$.

$A$ man can row at a speed of $10 \text{ km/h}$ in still water to a certain upstream point and back to the starting point in a river which flows at $4 \text{ km/h}$. Find his average speed for the total journey (in $\text{km/h}$).

$A$ boat covers $24 \, km$ upstream and $36 \, km$ downstream in $6 \, hours,$ while it covers $36 \, km$ upstream and $24 \, km$ downstream in $6 \frac{1}{2} \, hours.$ Then the velocity of the current is..........$km/h$

The speed of a boat along the stream is $12 \, km/h$ and against the stream is $8 \, km/h$. The time taken by the boat to sail $24 \, km$ in still water is: