SOLUTION: The current in a stream moves at a speed of 4 mph. A boat travels 5 mi upstream and 13 mi down stream in total time of 2 hr. What is the speed of the boat in still water?

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Question 386063: The current in a stream moves at a speed of 4 mph. A boat travels 5 mi upstream and 13 mi down stream in total time of 2 hr. What is the speed of the boat in still water?
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
time = distance / rate

[5 / (b - 4)] + [13 / (b + 4)] = 2

[5(b + 4)] + [13(b - 4)] = 2(b^2 - 16)

2b^2 - 32 - 5b - 20 - 13b + 52 = 0

b^2 - 9b = 0