SOLUTION: Junior's boat will go 15 mph in still water. If he can go 12 miles downstream in the same amount of time it takes to go 9 miles upsteam, then what is the speed of the current?

Question 159561: Junior's boat will go 15 mph in still water. If he can go 12 miles downstream in the same amount of time it takes to go 9 miles upsteam, then what is the speed of the current?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Junior's boat will go 15 mph in still water. If he can go 12 miles downstream
in the same amount of time it takes to go 9 miles upstream, then what is the
speed of the current?
:
Let the speed of the current = x
then
(15+x) = speed downstream
and
(15-x) = speed upstream
:
The times are give as equal, write a time equation from this fact
remember; Time =
:
Down stream time = Upstream time
=
Cross multiply, solve for x
9(15+x) = 15(15-x)
;
135 + 9x = 225 - 15x
:
9x + 15x = 225 - 135
:
24x = 90
x =
x = 3.75 mph is the speed of the current
;
;
Check solution by finding the times of each trip (add & subtract the current)
15/18.75 = .8 hrs
9/11.25 = .8 hrs, confirms our solution
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