$A$ boat takes half the time to travel a certain distance downstream compared to upstream. The ratio of the speed of the boat in still water to the speed of the current is:

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:

Speed of a boat is $5 \, km/h$ in still water and the speed of the stream is $3 \, km/h$. If the boat takes $3 \, h$ to go to a place and come back,the distance of the place is ....... $km$.

$A$ 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 $km/hr$).

$A$ man can row $9 \text{ km/hr}$ in still water. If the river is running at $3 \text{ km/hr}$,it takes $3 \text{ hours}$ more to row upstream than to row downstream for the same distance. How far is the place? (in $\text{km}$)

$A$ motor-boat can travel at $10 \, km/h$ in still water. It travelled $91 \, km$ downstream in a river and then returned to the same place,taking altogether $20 \, hours$. Find the rate of flow of the river (in $km/h$).