In a stream running at $2 \, km/hr$,a water scooter goes $10 \, km$ upstream and back again to the starting point in $55 \, minutes$. Find the speed of the water scooter in still water (in $km/hr$).

Twice the speed downstream is equal to thrice the speed upstream. The ratio of the speed in still water to the speed of the current is:

The speed of a boat in still water is $10\, km/h$. It covers an upstream distance of $45\, km$ in $6\, h$. The speed (in $km/h$) of the stream is:

$A$ 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 $km$)

Speed of a boat in standing water is $9 \text{ km/h}$ and the speed of the stream is $1.5 \text{ km/h}$. $A$ man rows to a place at a distance of $105 \text{ km}$ and comes back to the starting point. The total time taken by him is (in $\text{ hours}$)

$A$ sailor goes $12$ $km$ downstream in $48$ $min$ and returns in $1$ $h$ $20$ $min.$ The speed of the sailor in still water is..........$km/h$.