Question 810069: the speed of a stream is 2mph. A boat travels 7 miles upstream in the same time it takes 11 miles downstream. What is the speed of the boat in still water
Answer by TimothyLamb(4379)   (Show Source):
You can put this solution on YOUR website! s = d / t
t = d / s
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r = 2
7/(b - r) = 11/(b + r)
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7/(b - 12) = 11/(b + 12)
(b - 12)/7 = (b + 12)/11
b/7 - 12/7 = b/11 + 12/11
b/7 - b/11 = 12/7 + 12/11
b11/77 - b7/77 = 12*11/77 + 12*7/77
b4/77 = 216/77
b = 216/4 = 54
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boat speed in still water = 54 mph
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