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Math Help - Rate time distance

  1. #1
    CFY
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    Rate time distance

    An elevator went from the bottom to the top of a 240 m tower, remained there for 12 seconds, and returned to the bottom in an elapsed time of 2 minutes. If the elevator traveled 1 m/s faster on the way down, find its speed going up.
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  2. #2
    Senior Member MaxJasper's Avatar
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    Lightbulb Re: Rate time distance

    240/sup+12+240/(sup+1) = 2*60
    Last edited by MaxJasper; October 14th 2012 at 12:28 PM.
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  3. #3
    CFY
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    Re: Rate time distance

    thanks for your help. I tweaked your formaula a bit and found my answer; I was just unclear about what you meant by using "sup.:
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  4. #4
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    Re: Rate time distance

    Hello, CFY!

    An elevator went from the bottom to the top of a 240-m tower, remained there for 12 seconds,
    and returned to the bottom in an elapsed time of 2 minutes.
    If the elevator traveled 1 m/s faster on the way down, find its speed going up.

    Let S = speed going up (meters per second).
    Then S\!+\!1 = speed going down.

    The elevator went up 240 meters at S m/sec.
    . . This took: \frac{240}{S} seconds.

    Then it stopped for 12 seconds.

    Then it went down 240 meters at S\!+\!1 m/sec.
    . . This took: \frac{240}{S+1} seconds.


    The total time is 2 minutes (120 seconds).

    The equation is: . \frac{240}{S} + 12 + \frac{240}{S+1} \:=\:120


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    Nice "tweaking", CFY!
    You saw that Max meant: . \frac{240}{s_{up}} + 12 + \frac{240}{s_{up} + 1} \;=\;2\cdot60
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