$A$ man can row at the rate of $3.5 \, km/h$ in still water. If the time taken to row a certain distance upstream is $2 \frac{1}{2}$ times as much as the time taken to row the same distance downstream,find the speed of the current in $km/h$.

In one hour,a boat goes $11 \ km$ along the stream and $5 \ km$ against the stream. The speed of the boat in still water (in $km/hr$) is

$A$ man can row $6\, km/h$ in still water. If the speed of the current is $2\, km/h$,it takes $3\, hours$ more in upstream than in the downstream for the same distance. The distance is.....$km$.

$A$ man moves downstream at a rate of $14\, km/h$ and upstream at a rate of $6\, km/h$. The speed of the boat in still water is........$km/h$.

$A$ river is flowing with a steady speed of $4\, km/h$. One rows his boat downstream in the river and then returns by rowing upstream in the same river. When he returns to the starting point,the total distance covered by him is $42\, km$. If the return journey takes $2\, h$ more than his outward journey,then the speed of his rowing in still water must be (in $km/h$)

$A$ boat can travel with a speed of $13 \text{ km/hr}$ in still water. If the speed of the stream is $4 \text{ km/hr}$,the time taken by the boat to travel $63 \text{ km}$ in the opposite direction (upstream) is........$hrs$.