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Math Help - Related Rates

  1. #1
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    Related Rates

    Help guys!! I have no clue where to start this problem. Any help would be appreciated
    This is the problem.......

    At noon, ship A is 150 km west of ship B. Ship A is sailing east at 35 km/h and ship B is sailing north at 25 km/h. How
    fast is the distance between the ships changing at 4:00pm?
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  2. #2
    Junior Member Rheanna's Avatar
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    35x + 25x = 150
    ______________

    60x= 150

    _________

    = 2.5

    35(2.5) = 87.5 KM/H
    25(2.5) = 62.5 KM/H



    Hope I did this right.
    Last edited by Rheanna; November 2nd 2008 at 08:16 PM.
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  3. #3
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    ehhh I'm not too sure what you were doing there. Well I tried to solve this problem out and me and some other people got the the answer 28.36km/h which is incorrect. Can somebody please help me with this thanks.
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  4. #4
    Junior Member Rheanna's Avatar
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    Quote Originally Posted by Afterme View Post
    ehhh I'm not too sure what you were doing there. Well I tried to solve this problem out and me and some other people got the the answer 28.36km/h which is incorrect. Can somebody please help me with this thanks.

    just change the MPH to KM/H
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  5. #5
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    The final answer is 21.39km/h. Changing it to MPH has nothing to do with it.
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  6. #6
    Junior Member Rheanna's Avatar
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    Quote Originally Posted by Afterme View Post
    The final answer is 21.39km/h. Changing it to MPH has nothing to do with it.
    Guess, I'm stupider than I thought. Tried to help.
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  7. #7
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    Nah you're not stupid Thanks for the advice on converting Km/h to mph though, didn't know that =)
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  8. #8
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    At noon, ship A is 150 km west of ship B. Ship A is sailing east at 35 km/h and ship B is sailing north at 25 km/h. How
    fast is the distance between the ships changing at 4:00pm?

    distance equation

    x = square root of ((150-35t)square + (25t)square)

    dx/dt = rate of distance relative to time

    differentiate the other side

    and plug in 4 as time

    you will get 21.3933
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