$A$ boat covers a certain distance downstream in $2$ $hours$,but takes $4$ $hours$ to return upstream to the starting point. If the speed of the stream is $3$ $km/h$,find the speed of the boat in still water (in $km/h$).

$A$ boat takes half the time to travel a certain distance downstream compared to upstream. The ratio of the speed of the boat in still water to the speed of the current is:

From the given statements,decide which of the statement$(s)$ is/are necessary to answer the question.
What is the speed of a boat in still water?
$I.$ The boat covers $12 \text{ km}$ in $2 \text{ hours}$ downstream.
$II.$ The boat covers the same distance in $4 \text{ hours}$ upstream.
$III.$ The speed of the stream is $\frac{1}{3}$ that of the boat in still water.

In a stream running at $2 \ km/h$,a motorboat goes $6 \ km$ upstream and back again to the starting point in $33 \ minutes$. Find the speed of the motorboat in still water. (in $km/h$)

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 rows at $9 \frac{1}{3} \text{ km/h}$ in still water and finds that it takes him thrice as much time to row up than to row down the same distance in the river. The speed of the current is.......$\text{km/h}$