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 $\%$)

$A$ man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is:

$A$ person can row a certain distance downstream in $6$ $hours$ and return the same distance in $9$ $hours.$ If the stream flows at the rate of $2 \frac{1}{4} \text{ km/h},$ find how far he can row in an hour in still water (in $\text{km/h}$).

$A$ boat travels $18 \, km$ upstream in $6 \, hours$. How long (in $hours$) will it take to cover the same distance downstream if the speed of the current is one-fourth the speed of the boat in still water?

$A$ 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 $km$)

$A$ man can row $15\, km$ downstream in $3\, hours$ and $5\, km$ upstream in $2.5\, hours$. His speed in still water in $(km/hr)$ is: