Question
Debbie traveled by boat 5miles upstream to fish in her favourite spot> Because of the 4-mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water ????
Please help !!!!!!!!!!!!!!
Please help !!!!!!!!!!!!!!
Answers
drwls
Let V be the speed in still water, in mph. The speed with respect to land will be V-4 upstream and V+4 downstream.
Upstream travel time (in hours) = Downstream travel time + 1/3 hour.
5/(V-5) - 5/(V+5) = 1/3
Solve for V
[5(V+5) - 5(V-5)]/(V^2 -25) = 1/3
50/(V^2-25) = 1/3
150 = V^2 -25
V = sqrt 175 = 13.23 mph
Upstream travel time (in hours) = Downstream travel time + 1/3 hour.
5/(V-5) - 5/(V+5) = 1/3
Solve for V
[5(V+5) - 5(V-5)]/(V^2 -25) = 1/3
50/(V^2-25) = 1/3
150 = V^2 -25
V = sqrt 175 = 13.23 mph