SOLUTION: distance,speed, and time.
It took a crew 2 hours and 40mins. to row 6km upstream and back again. If the rate of flow of the stream was 3km/hr, what was the rowing speed of the cre
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Question 212693This question is from textbook
: distance,speed, and time.
It took a crew 2 hours and 40mins. to row 6km upstream and back again. If the rate of flow of the stream was 3km/hr, what was the rowing speed of the crew in still water?
This question is from textbook
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
distance,speed, and time.
It took a crew 2 hours and 40mins. to row 6km upstream and back again. If the rate of flow of the stream was 3km/hr, what was the rowing speed of the crew in still water?
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Upstream DATA:
distance = 6 km ; rate = b-3 km ; time = 6/(b-3) hrs
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Downstream DATA:
distance = 6 km ; rate = b+3 km ; time = 6/(b+3) hrs
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Equation:
time + time = 2 2/3 hrs
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6/(b-3) + 6/(b+3) = 8/3 hrs
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Multiply thru by 3(b-3)(b+3) to get:
6*3(b+3) + 6*3(b-3) = 8(b^2-9)
18b + 18b = 8b^2 - 72
8b^2 - 36b - 72 = 0
2b^2 - 9b - 18 = 0
(b-6)(2b+3) = 0
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Positive solution:
b = 6 km (speed of the boat in still water)
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Cheers,
Stan H.
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