SOLUTION: a boat can travel 9 miles up a river in the same amount of time it takes to travel 11 miles down the same river. if the current is 2 miles per hour, what is the speed of the boat i

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: a boat can travel 9 miles up a river in the same amount of time it takes to travel 11 miles down the same river. if the current is 2 miles per hour, what is the speed of the boat i      Log On


   

Question 117497: a boat can travel 9 miles up a river in the same amount of time it takes to travel 11 miles down the same river. if the current is 2 miles per hour, what is the speed of the boat in still water ?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
a boat can travel 9 miles up a river in the same amount of time it takes to travel 11 miles down the same river. if the current is 2 miles per hour, what is the speed of the boat in still water ?
:
Let s = speed in still water
then
(x+2) = speed downstream
and
(x-2) = speed upstream
:
The times for the two trip are give as equal, write time equaion:
Time = Dist/speed:
:
Upriver time = downriver time
9%2F%28%28s-2%29%29 = 11%2F%28%28s%2B2%29%29
:
Cross multiply
11(s-2) = 9(s+2)
11s - 22 = 9s + 18
11s - 9s = 18 + 22
2s = 40
s = 40/2
s = 20 mph speed in still water
:
:
Check solution to confirm that the times are equal
11/22 = .5
9/18 = .5