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Math Help - Ration expression word problem please help!

  1. #1
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    Ration expression word problem please help!

    Jay Flew his airplane 500km against the wind in the same time it took him to fly 600km with the wind. The speed of the wind was 20km/h. What was the average speed of the airplane?

    I use S as the speed of the airplane

    I got 500/s-20km per hour = 600/s+20km per hour, but could get no further. Please help!
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  2. #2
    Super Member bigwave's Avatar
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    Quote Originally Posted by Skdch View Post
    Jay Flew his airplane 500km against the wind in the same time it took him to fly 600km with the wind. The speed of the wind was 20km/h. What was the average speed of the airplane?

    I use S as the speed of the airplane

    I got 500/s-20km per hour = 600/s+20km per hour, but could get no further. Please help!
    your formula is fine but
    will change your variable s to R since

    Rate = \frac{Time}{Distance}

    \frac{500}{R-20} = \frac{600}{R+20}

    cross multiply

    600(R-25) = 500(R+25)

    distribute

    600R-600(25) = 500R + 500(25)

    collect like terms and combine

    100R = 600(25) + 500(25)

    divide all terms by 100

    R = (6)(25) + 5(25) = 375km/h
    Last edited by bigwave; January 10th 2010 at 04:57 PM. Reason: equation correction
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