$A$ man rows a boat $18 \ km$ in $4 \ h$ downstream and returns upstream in $12 \ h$. The speed of the stream (in $km/h$) is

$A$ man can row $30 \text{ km}$ upstream and $44 \text{ km}$ downstream in $10 \text{ hours}$. Also,he can row $40 \text{ km}$ upstream and $55 \text{ km}$ downstream in $13 \text{ hours}$. Find the rate of the current and the speed of the man in still water (in $\text{km/h}$).

$A$ man can row upstream $36 \text{ km}$ in $6 \text{ hours}$. If the speed of a man in still water is $8 \text{ km/hr}$,find how much distance he can cover downstream in $10 \text{ hours}$? (in $\text{km}$)

$A$ 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 $\text{km}$)

If a man's rate with the current is $12 \text{ km/h}$ and the rate of the current is $1 \frac{1}{2} \text{ km/h}$,then his rate against the current is ...... $\text{km/h}$.

The ratio of the speed of a motorboat to that of the water current is $36 : 5$. The motorboat travels along with the current in $5 \, h \, 10 \, min$. Find the time taken by the motorboat to return.