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Math Help - grade 10 word problems (speed, time, distance)

  1. #1
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    Exclamation grade 10 word problems (speed, time, distance)

    question: An airplane has a speed of 250km/hour. One day it flies 990 kms with a tailwind, and then returns against the wind. The total trip-time is 8 hours. Find the velocity of the wind (assume it is constant).

    I honestly just completely dont get this question, i dont find that the wind speed has any relevance to the question since going with and against the wind speed would just cancel itself out :S

    Any help is greatly appreciated
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  2. #2
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    maybe this can point u in the right direction

    250km/h*8h=2000km
    (2*990km)/8h=247.5km/h

    But I don't get this part: "An airplane has a speed of 250km/hour."

    What speed is it?
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  3. #3
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    Quote Originally Posted by sodapop12345 View Post
    question: An airplane has a speed of 250km/hour. One day it flies 990 kms with a tailwind, and then returns against the wind. The total trip-time is 8 hours. Find the velocity of the wind (assume it is constant).

    I honestly just completely dont get this question, i dont find that the wind speed has any relevance to the question since going with and against the wind speed would just cancel itself out :S

    Any help is greatly appreciated
    Let the wind speed by v km/hr.

    With the tail wind the plane is moving at (250 + v) km/hr.
    Against the wind the plane is moving at (250 - v) km/hr.

    Time = distance/speed. Therefore total time of round trip is:

    8 = \frac{990}{250 + v} + \frac{990}{250 - v}.

    Solve this equation for v.

    I get v = 25.
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