$A$ man swims downstream a distance of $15\, km$ in $1\, h$. If the speed of the current is $5\, km/h$,the time taken by the man to swim the same distance upstream is

$A$ 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 $km/h$.

Speed of a motorboat in still water is $45 \text{ km/h}$. If the motorboat travels $80 \text{ km}$ along the stream in $1 \text{ h } 20 \text{ min}$,then the time taken by it to cover the same distance against the stream will be:

$A$ man can row at $5 \, km/h$ in still water and the velocity of the current is $1 \, km/h$. It takes him $1 \, hour$ to row to a place and back. How far is the place? (in $km$)

$A$ boat travels $2\, km$ upstream in a stream flowing at $3\, km/h$ and then returns downstream to the starting point in $30\, minutes$. The speed of the boat in still water is........$km/h$.

$A$ boat goes $13\, km$ upstream in $39\, minutes$. The speed of the stream is $3\, km/h$. The speed of the boat in still water is......$km/h$.