SOLUTION: Upstream, downstream. Junior’s boat will go 15 miles per hour in still water. If he can go 12 miles downstream in the same amount of time as it takes to go 9 miles upstream, then w

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Question 174061: Upstream, downstream. Junior’s boat will go 15 miles per hour in still water. If he can go 12 miles downstream in the same amount of time as it takes to go 9 miles upstream, then what is the speed of the current?
Answer by stanbon(48558) About Me  (Show Source):
You can put this solution on YOUR website!
Junior’s boat will go 15 miles per hour in still water. If he can go 12 miles downstream in the same amount of time as it takes to go 9 miles upstream, then what is the speed of the current?
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Downstream DATA;
distance = 12 miles; rate = 15+c mph ; time = d/r = 12/(15+c) hrs.
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Upstream DATA:
distance = 9 miles ; rate = 15-c mph ; time = d/r = 9/(15-c) hrs.
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Time = time
12/(15+c) = 9/(15-c)
12(15-c) = 9(15+c)
12*15 - 12c = 9*15 + 9c
21c = 3*15
c = 3*15/21
c = 45/21 = 2.1429..(speed of the current)
Cheers,
Stan H.