Question 815697: A boat takes 2/3 as much time to travel downstream as to return. If the rate of the current is 8 kph, what is the rate 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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w = 8 kph
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d/(b + w) = (2/3)d/(b - w)
1/(b + w) = (2/3)/(b - w)
1/(b + w) - (2/3)/(b - w) = 0
(b - w)/(b + w)(b - w) - (2/3)(b + w)/(b + w)(b - w) = 0
( (b - w) - (2/3)(b + w) ) = 0(b + w)(b - w)
b - w - (2/3)b - (2/3)w = 0
(3/3)b - (2/3)b - (2/3)w - (3/3)w = 0
(1/3)b - (5/3)w = 0
(1/3)b - (5/3)8 = 0
b = (5/3)8(3/1)
b = (5)8
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b = 40 kph
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