A plane takes hours to fly to its destination against the wind.

The return trip takes hours it takes to its source.

The planes avaerage speed in still air is .

Find what is the average speed of the wind during the flight.

Let the average speed of the wind be miles per hour.

Find the speeds of the plane against and with the wind.

Its average speed in still air is

Thus,speed against the wind is and speed with the wind is .

Formula for distance is .

Distance against the wind  is

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Distance with the wind is

\

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The distances going and coming are equal.

\

Therefore,

\

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             (Distributive property: )

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                    (Simplify)

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(Add to each side)

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                                 (Apply additive inverse property: )

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        (Subtract from each side)

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                                                (Apply additive inverse property: )

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                                           (Divide each side by )

\                          (Cancel common terms) \

Therefore, the average speed of the wind is . 

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The average speed of the wind is .