SOLUTION: Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of t
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Question 101185: Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of the river's current?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of the river's current?
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Let the river rate be "c".
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Down stream DATA:
Rate = 30+c ; distance = 7 mi ; time = d/r = 7/(30+c)
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Up stream DATA:
Rate = 30-c ; distance = 3 mi : time = d/r = 3/(30-c)
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EQUATION:
7/(30+c) = 3/(30-c)
210-7c = 90+3c
10c = 30
c = 3 mph (speed of the current)
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Cheers,
Stan H.
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