<PRE><B>Question 675455</B>
Bob travels 4 miles upstream. In the same time, he could have traveled 7 miles downstream. If the speed of the current is 3 mph, find the speed of the boat in still water.
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let x=speed of the boat in still water
x-3=speed upstream
x+3=speed downstream
travel time=distance/speed (same for upstream and downstream travel)
4/(x-3)=7/(x+3)
4x+12=7x-21
3x=33
x=11
speed of the boat in still water=11 mph</PRE>