Question 988734
Upstream, downstream, Katherine's boat will go 15 miles per hour in still water. If she can go 12 miles down stream in the same time it takes to go 9 miles upstream, then what is the speed of the current 
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Downstream DATA:
dist = 12 miles ; rate = 15+c mph ; time = d/r = 12/(15+c) hrs
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Upstream DATA:
dist =  9miles ; rate = 15-c mph ; time = d/r = 9/(15-c) hrs
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Equation:
time = time
12/(15+c) = 9/(15-c)
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12(15-c) = 9(15+c)
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12*15 - 12c = 9*15 + 9c
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21c = 3*15
c = (1/7)15
c = 2 1/7 mph (speed of the current)
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Cheers,
Stan H.
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