SOLUTION: Please explain: The excursion boat on the river takes 2.5 hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water i

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Question 430978: Please explain:
The excursion boat on the river takes 2.5 hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate the river current, what is the rate of the current?
Whis equation can be used to solve for c?
(4c)(2.5) + (6c)(2.5) =24
(4c)(2.5) + (6c)(24) =2.5
[12/(4c)] +[12/(6c)] =2.5

Answer by htmentor(1343) About Me  (Show Source):
You can put this solution on YOUR website!
Let s = the speed in still water
Let c = the speed of the current
The speed on the upstream trip will be: s - c
The speed on the downstream trip will be: s + c
The total time required is the sum of the upstream and downstream times:
t = t_up + t_down = d%2F%28s-c%29+%2B+d%2F%28s%2Bc%29
Given: t = 2.5 hr, s = 5c, d = 12 mi
Therefore we have the following expression for the total time:
2.5+=+12%2F%285c-c%29+%2B+12%2F%285c%2Bc%29
This simplifies to:
2.5+=+12%2F4c+%2B+12%2F6c