A motorboat can row at the speed of 8 km/hr in still water. If the speed of current is 2 km/hr and the boat takes 4 hours to row to a place and return back, how far is the place

15 km

The correct answer is Option (3) → 15 km

Time taken to go downstream = $\frac{d}{10}$

Time taken to return upstream = $\frac{d}{6}$

$⇒\frac{d}{6}+\frac{d}{10}=4$

$⇒\frac{8d}{30}=4$

$⇒d=15km$