$A$ motor boat,whose speed is $15 \text{ km/hr}$ in still water,goes $30 \text{ km}$ downstream and comes back in a total of $4 \text{ hours } 30 \text{ minutes}$. The speed of the stream (in $\text{km/hr}$) is:

If a man's rate with the current is $12\, km/h$ and the rate of current is $1.5\, km/h$,then the man's rate against the current in $km/h$ is...........

$A$ boat covered a certain distance travelling downstream in $45$ $minutes,$ while it came back to the starting point in $1$ $hour$ $15$ $minutes.$ The speed of the stream is $2$ $kmph.$ What is the speed of the boat in still water? (in $kmph$)

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 $9\, km/h$ and the speed of the stream is $1.5\, km/h$. $A$ man rows to a place at a distance of $105\, km$ and comes back to the starting point. What is the total time taken by him?

What time will be taken by a boat to cover a distance of $128\, km$ along the stream,if the speed of a boat in still water is $24\, km/h$ and the speed of the stream is $8\, km/h$? (in $h$)