SOLUTION: I am not sure how to figuere out the answer to these two questions: 21.) The makimum speed of a barge in still water is 8 miles per hour. At this rate, a 30 mile trip downstream (

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: I am not sure how to figuere out the answer to these two questions: 21.) The makimum speed of a barge in still water is 8 miles per hour. At this rate, a 30 mile trip downstream (      Log On


   

Question 636940: I am not sure how to figuere out the answer to these two questions:
21.) The makimum speed of a barge in still water is 8 miles per hour. At this rate, a 30 mile trip downstream (with the current) takes as much time as an 18 mile trip upstream (against the current).
A. Find the rational expressions that measure the amount of time it takes for the barge to go downstream and upstream if c represents the speed of the current.
B. What is the speed of the current?
Please tell me what I should do on this question.
Thank you Tim
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The makimum speed of a barge in still water is 8 miles per hour. At this rate, a 30 mile trip downstream (with the current) takes as much time as an 18 mile trip upstream (against the current).
A. Find the rational expressions that measure the amount of time it takes for the barge to go downstream and upstream if c represents the speed of the current.
Downstream DATA:
distance = 30 miles ; rate = 8+c ; time = 30/(8+c) hrs
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Upstream DATA:
distance = 18 miles ; rate = 8-c ; time 18/(8-c) hrs
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Equation:
time up = time down
18/(8-c) = 30/(8+c)
18(8+c) = 30(8-c)
144 + 18c = 240 - 30c
48c = 96
c = 2 mph (speed of the current)
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Cheers,
Stan H.
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B. What is the speed of the current?