$A$ boatman rows $1\, km$ in $5\, min$ along the stream and $6\, km$ in $1\, h$ against the stream. The speed of the stream is $km/h$.

In a river,the ratio of the speed of the stream to the speed of a boat in still water is $2:5$. In another case,the ratio of the speed of the stream to the speed of a boat in still water is $3:4$. What is the ratio of the speeds of the first boat to the second boat in still water?

$A$ man can row $40\, km$ upstream and $55\, km$ downstream in $13\, hours$. Also,he can row $30\, km$ upstream and $44\, km$ downstream in $10\, hours$. Find the speed of the man in still water and the speed of the current.

The speed of a boat downstream is $\frac{16}{9}$ times the speed of the boat upstream. The speed of the current is what percent of the speed of the boat in still water? (in $\%$)

$A$ boat covers $24 \text{ km}$ upstream and $36 \text{ km}$ downstream in $6 \text{ hours}$,while it covers $36 \text{ km}$ upstream and $24 \text{ km}$ downstream in $6 \frac{1}{2} \text{ hours}$. The velocity of the current is .... $\text{km/h}$.

$A$ motor-boat,travelling at the same speed,can cover $25\, km$ upstream and $39\, km$ downstream in $8\, hours$. At the same speed,it can travel $35\, km$ upstream and $52\, km$ downstream in $11\, hours$. The speed of the stream is $........\, km/h$.