SOLUTION: a boat travels 45 mi upstream (against the current) in 5h. The boat travels the same distance downstream in 3h. What is the rate of the current?

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Question 922685: a boat travels 45 mi upstream (against the current) in 5h. The boat travels the same distance downstream in 3h. What is the rate of the current?
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
a boat travels 45 mi upstream (against the current) in 5h. The boat travels the same distance downstream in 3h. What is the rate of the current?
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let x=rate of boat in still water
let c=rate of current
(x+c)=rate of boat downstream
(x-c)=rate of boat upstream
distance/rate=travel time
45/(x-c)=5
45/(x+c)=3
..
5x-5c=45
3x+3c=45
..
15x-15c=135 (mult. eq by 3)
15x+15c=225 (mult. eq by 5)
subtract:
-30c=-90
c=3
What is the rate of the current? 3 mph