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

15 km

The correct answer is option (2) : 15 km

$x= 8\, km/h$

$y = 2\, km/h$

$t = 4\, hrs $

$∵ d=\frac{t(x^2-y^2)}{2x}=\frac{4(8^2-2^2)}{2×8}$

$=\frac{60}{4}=15\, km$

Hence, the place is 15 km apart.