$A$ man can row at a speed of $15\, km/hr$ in still water to a certain upstream point and back to the starting point in a river which flows at $3\, km/hr$. Find his average speed for the total journey (in $km/hr$).

$A$ 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 $km$).

Speed of boat in still water is $5\, km/h$. While river is flowing with a speed of $2\, km/h$ and time taken to cover a certain distance upstream is $2\, h$ more than time taken to cover the same distance downstream. Find the distance (in $km$).

When the speed of a boat in still water is $4\, km/h$ and the rate of stream is $2\, km/h$,find the upstream speed of the boat (in $km/h$).

$A$ person can row a certain distance downstream in $6$ $hours$ and return the same distance in $9$ $hours.$ If the stream flows at the rate of $2 \frac{1}{4} \text{ km/h},$ find how far he can row in an hour in still water (in $\text{km/h}$).

$A$ boat covers a certain distance downstream in $1 \text{ hour}$,while it comes back in $1.5 \text{ hours}$. If the speed of the stream is $3 \text{ km/hr}$,what is the speed of the boat in still water? (in $\text{km/hr}$)