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Homework Help: Not sure what subject this comes under, and not HW, just a problem.

  1. Jun 25, 2009 #1
    1. The problem statement, all variables and given/known data
    A plane travelling a distance of 660km, with unknown speed, has a tail wind of 60km/h, and due to this tail wind arrives at its destination 6 mins early.

    What is the speed of the plane without the wind?

    2. Relevant equations
    I have so far used s=d/t,

    3. The attempt at a solution
    Using s=d/t, i have got expressions for both s and t.

    s = (x + 16.7) m/s
    t = (x' +360) s and i have converted 660 km into metres, 660000m to get

    x + 16.7 = 660000/(x' + 360)

    However i am not sure if this is the right way of looking at it, so any help will be greatly appriechiated.

  2. jcsd
  3. Jun 25, 2009 #2


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    Science Advisor

    Where is the "16.7" from?

    Why convert to meters?
    Let v be the speed, in km/h, without the wind, t the time, in hours, to make the trip without the wind. Then 660/t= v or vt= 660. With the tail wind the speed is v+ 60 and the time for the trip is t- 1/10 (60 minutes is 1/10 hour). Then 660/(t- 1/10)= v+ 60 or 660= (t- 1/10)(v+ 60)= tv+ 60t+ v/10+ 6.

    Solve the two equations vt= 660 and tv+ 60t+ v/10+ 6= 660.
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