Question 1187161
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A man travels at 4km/h in still water. If the speed of water current is 1 km/h.
It takes 4 hours to reach the place and come back. How far is the place?
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<pre>
The effective speed traveling downstream is 4 km/h + 1 km/h = 5 km/h;

The effective speed traveling   upstream is 4 km/h - 1 km/h = 3 km/h.


Let d be the one way distance, in kilometers.


The travel time downstream is  {{{d/5}}}  hours;  upstream  {{{d/3}}}  hours.


The total time is 4 hours, giving the "time" equation


    {{{d/5}}} + {{{d/3}}} = 4.


To solve it, multiply both sides by 5*3 = 15.  You will get then


    3d + 5d = 4*15

      8d    = 60

       d    = 60/8 = 7.5 kilometers.


<U>ANSWER</U>.  One way distance is 7.5 kilometers.


<U>CHECK</U>.   {{{7.5/5}}} + {{{7.5/3}}} = 1.5 + 2.5 = 4 hours.    ! Correct !
</pre>

Solved.