Posted by mo on Saturday, September 22, 2007 at 9:54am.
Debbie traveled by boat 5miles upstream to fish in her favourite spot> Because of the 4mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water ????
Please help !!!!!!!!!!!!!!

MaTh  drwls, Saturday, September 22, 2007 at 11:18am
Let V be the speed in still water, in mph. The speed with respect to land will be V4 upstream and V+4 downstream.
Upstream travel time (in hours) = Downstream travel time + 1/3 hour.
5/(V5)  5/(V+5) = 1/3
Solve for V
[5(V+5)  5(V5)]/(V^2 25) = 1/3
50/(V^225) = 1/3
150 = V^2 25
V = sqrt 175 = 13.23 mph