Question 982639


Let &nbsp;<B>u</B>&nbsp; be the rower's speed in still water in kilometers per hour &nbsp;({{{km/h}}}).

Since the river floats with a current of &nbsp;2 {{{km/h}}}, &nbsp;the rower's speed is &nbsp;<B>u</B>-2 {{{km/h}}} &nbsp;relative to the bank of the river, &nbsp;when the man rows upstream. &nbsp;It gives you an equation 

{{{16/(u-2)}}} = {{{4}}}.


Hence, &nbsp;u - 2 = {{{16/4}}} = 4 {{{km/h}}}. 

Therefore, &nbsp;u = 4 + 2 = 6 {{{km/h}}} &nbsp;(the rower's speed in still water). 

It implies that the rower's speed is &nbsp;<B>u</B>+2 = 6 + 2 = 8 {{{km/h}}} &nbsp;relative to the bank of the river, &nbsp;when the man rows downstream.


It means that the way downstream will take &nbsp;{{{16/8}}} = 2 hours.


<B>Answer</B>. The return trip will take &nbsp;2&nbsp; hours.