SOLUTION: The mad river flows at a rate of 2 KM/H. In order for a boat to travel 79.2 KM of River and then return in a total of eight hours how fast must about travel in Still water?

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Question 863852: The mad river flows at a rate of 2 KM/H. In order for a boat to travel 79.2 KM of River and then return in a total of eight hours how fast must about travel in Still water?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The mad river flows at a rate of 2 KM/H. In order for a boat to travel 79.2 KM of River and then return in a total of eight hours how fast must about travel in Still water?
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with current DATA:
distance = 39.6 km ; rate = b + 2 km/hr ; time = 39.6/(b+2) hrs
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against current DATA:
distance = 39.6 km ; rate = b - 2 km/hr ; time = 39.6/(b-2) hrs
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Equation:
time + time = 8 hrs
39.6/(b+2) + 39.6/(b-2) = 8
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2(39.6)b = 8(b^2-4)
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4(b^2-4) = 39.6b
4b^2 - 39.6b - 16 = 0
b = 10.29 km/hr (speed of the boat in still water)
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Cheers,
Stan H.