SOLUTION: The current in a stream moves at a speed of 5 km/h. A boat travels 39 km upstream and 39 km downstream in a total time of 12 hours. What is the speed of the boat in still water?
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Question 890364: The current in a stream moves at a speed of 5 km/h. A boat travels 39 km upstream and 39 km downstream in a total time of 12 hours. What is the speed of the boat in still water?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
d = r*t
t = d/r
39/(b+5) + 39/(b-5) = 12
13/(b+5) + 13/(b-5) = 4
15(b+5) + 13(b-5) = 4(b^2-5)
26b = 4b^2 - 20
2b^2 - 13b - 10 = 0
Solve for b
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