SOLUTION: It took a bird the same amount of time to fly 10 miles with wind as 5 miles against the wind. What is the speed of the wind if the bird flies 30 mph in still air?

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Question 1197131: It took a bird the same amount of time to fly 10 miles with wind as 5 miles against the wind. What is the speed of the wind if the bird flies 30 mph in still air?
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
It took a bird the same amount of time to fly 10 miles with wind as 5 miles against the wind. What is the speed of the wind if the bird flies 30 mph in still air?
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Airspeed of the bird = 30 mi/hr
w = windspeed
5(30 - w) = 10(30 + w)
30 - w = 60 + 2w
3w = 30
w = 10 mi/hr
Answer by ikleyn(52790)   (Show Source): You can put this solution on YOUR website!
.

Let w be the rate of the wind.


Write the "time" equation as you read the problem

     = .


Here 30+w is the effective speed with the wind 

and  is the time to fly 10 miles with the wind,

so it explains left side of the equation.



Right side describes the time flying 5 miles against the wind.



From this equation, by cross-multiplying, you get

    10*(30-w) = 5*(30+w)

    300 - 10w = 150 + 5w

    300 - 150 = 10w + 5w

       150    =    15w

         w    =    150/15 = 10 miles per hour.    ANSWER

Solved.


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