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 $\%$)

The speed of a boat in still water is $6\, km/h$ and the speed of the stream is $1.5\, km/h$. $A$ man rows to a place at a distance of $22.5\, km$ and returns to the starting point. The total time taken by him is:

Two boats $A$ and $B$ start towards each other from two places,$108 \text{ km}$ apart. The speeds of boats $A$ and $B$ in still water are $12 \text{ km/h}$ and $15 \text{ km/h}$,respectively. If $A$ proceeds down the stream and $B$ proceeds up the stream,they will meet after .......... $\text{h}$.

The speed of a boat in still water is $7\, km/h$. If its speed in downstream is $10\, km/h$,then the speed of the stream is .......... $km/h$.

$A$ person takes total $5$ $hours$ to go to a destination downstream and come back upstream by boat. If the speed of the boat in still water is $10 \text{ km/h}$ and the speed of the stream is $4 \text{ km/h}$,what is the distance of the destination from the starting point (in $\text{km}$)?

$A$ 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 $kmph$)