The speed of boat in still water is 15kmph and the rate of current is 3kmph. The distance travelled downstream in 12 minutes

Let speed of boat in still water $x=\text{15kmph}$

Speed of current $y=3\text{kmph}$

Down stream speed $=x+y$

                                 $=15+3=18\text{kmph}$

Time$=\text{12 min}$

$\text{=}\frac{\text{12}}{60}\text{hours}$

$\text{=}\frac{1}{5}\text{hours}$

$\therefore$ Distance$=\text{Speed×Time}$

                    $=18\times \frac{1}{5}=3.6\text{km}$