$A$ boat moves downstream at the rate of $1 \, km$ in $10 \, minutes$ and upstream at the rate of $4 \, km/h$. What is the velocity of the current (in $km/h$)?

$A$ boat goes $6\, km$ upstream and back again to the starting point in $2\, hours$. If the velocity of the stream is $4\, km/hr$,what is the speed of the boat in still water? (in $km/hr$)

$A$ boat takes $90$ minutes less to travel $36$ miles downstream than to travel the same distance upstream. If the speed of the boat in still water is $10$ miles/hour,the speed of the stream is.......miles/hour.

$A$ man can row $20 \text{ km/h}$ in still water and the speed of the stream is $5 \text{ m/s}$. The ratio of the speed of the man to the speed of the current is:

In a stream running at $2 \ km/h$,a motorboat goes $6 \ km$ upstream and back again to the starting point in $33 \ minutes$. Find the speed of the motorboat in still water. (in $km/h$)

$A$ man can row three-quarters of a kilometre against the stream in $11 \frac{1}{4}$ minutes. The speed (in $km/hr$) of the man in still water is