SOLUTION: a boat traveled 45 miles downstream in 5 hours. the return trip took 9 hours upstream. what is the rate of the boat in still water in miles per hour?

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Question 400516: a boat traveled 45 miles downstream in 5 hours. the return trip took 9 hours upstream. what is the rate of the boat in still water in miles per hour?
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
Let x(mph)= the rate of the boat in still water
Let y mph = the rate of the river
When boat travels downstream the rate is (x+y)mph
From text:a boat traveled 45 miles downstream in 5 hours, so boat (downstream ) rate was 45%2F5=9 mph
We have the first equation of system
x%2By=9
When boat travels upstream the rate is (x-y) mph
From text:a boat traveled 45 miles downstream in 9 hours, so boat (upstream ) rate was 45%2F9=5 mph
the second equation is
x-y=5%29%29%29%0D%0ASolve+the+system%0D%0A%7B%7B%7Bx%2By=9
x-y=5%29%29%29%0D%0AAdd+the+first+equation+to+the+second%0D%0A%7B%7B%7B2x=14
x=14%2F2
x=7 mph - the rate of the boat in still water
Answer 7 mph