SOLUTION: I am having problems figuring this problem out, Juniors boat will go 15 miles per hour in still water. If he can go 12 miles downstream in the same amount of time as it takes t

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Question 283318: I am having problems figuring this problem out,
Juniors boat will go 15 miles per hour in still water. If he can go 12 miles downstream in the same amount of time as it takes to go 9 miles upstream, then what is the speed of the current?
can you please help me, and explain the steps. thank you.

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
r*t=d
(15+c)*t=12
(15-c)*t=9

t=12/(15+c)
t=9/(15-c)
12/(15+c)=9/(15-c)
4/(15+c)=3/(15-c)
4*(15-c)=3*(15+c)
60-4c=45+3c
15=7c
c = 15/7=2 1/7 mph
t = 7/10*60=42 minutes