SOLUTION: In still water, a paddle boat averages 20 miles per hour. It takes the boat the same amount of time to travel 72 miles downstream, with the current, as 48 miles upstream, against t

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Question 819934: In still water, a paddle boat averages 20 miles per hour. It takes the boat the same amount of time to travel 72 miles downstream, with the current, as 48 miles upstream, against the current. What is the rate of the water's current?
Answer by TimothyLamb(4379) About Me  (Show Source):
You can put this solution on YOUR website!
s = d / t
t = d / s
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down:
t = 72/(20 + w)
up:
t = 48/(20 - w)
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72/(20 + w) = 48/(20 - w)
72(20 - w)/(20 - w)(20 + w) - 48(20 + w)/(20 - w)(20 + w) = 0
72(20 - w) - 48(20 + w) = 0(20 - w)(20 + w)
1440 - 72w - 960 - 48w = 0
480 = 120w
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w = 4 mph
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