Question 1180881
.
<pre>

If the boat can be rowed at 4 times the speed of the current, then its speed upstream is 4r - r = 3r,
where "r" is the rate of the current.



Then for "r" you have this distance equation

    6 hours * 3r mph = 18 miles, 

which gives the <U>ANSWER</U>  r = 18/(6*3) = 1 mph for the rate of the current and  4*1 = 4  mph for the rate of the boat in still water.



In this problem, ONLY ONE condition is necessary:  EITHER  for upstream travel  OR  for downstream travel.



To have these two conditions is UNNECESSARY and EXCESSIVE LUXURY in this problem.
</pre>

Solved, answered and explained.