$A$ boat goes $40\, km$ upstream in $8\, h$ and $36\, km$ downstream in $6\, h$. The speed of the boat in still water is......$km/h$

$A$ man can row at $5 \text{ km/hr}$ in still water. If the velocity of the current is $1 \text{ km/hr}$ and it takes him $1 \text{ hour}$ to row to a place and come back,how far is the place? (in $\text{km}$)

$A$ boat travels upstream from $B$ to $A$ and downstream from $A$ to $B$ in $3$ $hours$. If the speed of the boat in still water is $9\, km/h$ and the speed of the current is $3\, km/h$,the distance between $A$ and $B$ is........$km$.

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

$A$ boatman takes twice as long to row a distance against the stream as to row the same distance with the stream. Find the ratio of the speed of the boat in still water to the speed of the stream.

$A$ steamer goes downstream from one port to another in $4\, h$. It covers the same distance upstream in $5\, h$. If the speed of the stream is $2\, km/h$,then find the distance between the two ports (in $km$).