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Thread: My stupid math teacher...

  1. #1
    Future USMC Cobra Pilot Member Prussian to the Iron's Avatar
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    Default My stupid math teacher...

    Alright, so on a worksheet today, she worked out a simple math problem. Or so she thought. Upon closer inspection, her answer is completely wrong, in addition to the question not having any sort of non-decimal answer.

    The Question:

    Given: 6 times (X^2)=36
    X^3=?

    Her answer:

    X^3=3 times cubed root of 8

    Her answer is obviously wrong. first off, cubed root of 8 is 2. no matter, it comes out to 6 either way.
    second, if you take the cubed root of 6 (in order to get X to the 1st power), it comes out to 1.81712059. This squared, to come out with X squared (as in the first part of the problem), multiplied by 6, does NOT come out to 36.
    in fact, nothing squared times 6 equals 36 (except, obviously, the square root of 6, rather than the CUBED root)

    Perhaps I'm missing something, but if anyone works this out and finds that it does in fact come out as X cubed equals 6, but at the same time X squared times 6 equals 36, please tell me how, because apparently I'm lost.

    I know I'm right, I just want to see if I missed something.
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  2. #2
    Senior Member Senior Member gaelic cowboy's Avatar
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    Default Re: My stupid math teacher...

    This has to be a mistake teacher probably meant to write X^2 not X^3 unless you left some of the question out???

    answer is X^2=6 for me anyway and if they are really looking for X^3 then the answer is 6 x (sqrroot6)

    But my money is on a simple mistake in writing the question and that it is supposed to be X^2
    Last edited by gaelic cowboy; 10-15-2010 at 12:30.
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  3. #3

    Default Re: My stupid math teacher...

    As stated, there are two solutions to the problem. First of all x = 36/6 (hence x = 6), has two solutions: x= sqrt(6), or x = - sqrt(6). As a result x = - (6^(3/2)), or x = 6^(3/2).

    But we can simplify the answers above for 6 = 3 *2.
    So 6^(3/2) = (3^(3/2)) * (2 ^(3/2)) = 3*sqrt(3) * 2*sqrt(2) = sqrt(27) * sqrt(8) = sqrt(216). (Through various identities on powers.)
    EDIT: Plug these simplifications in the answer:
    x = sqrt(216), or x = - sqrt(216).

    EDIT2: The simplification is mainly to show that the 8 your teacher got might not be a random figure pulled out of the air, we can see there is a sqrt(8) component to the answer too. Of course if you're good with the arithmetic it's faster to write 6^(3/2) = sqrt(6^3) = sqrt(216).
    Last edited by Tellos Athenaios; 10-15-2010 at 14:06.
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  4. #4
    Senior Member Senior Member gaelic cowboy's Avatar
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    Default Re: My stupid math teacher...

    http://www.xamuel.com/plus-or-minus-square-roots/


    Oh just on a side note Prussian Iron in case your confused 6 * (sqrt6) is the same as sqrt(216)

    Tellos makes a good point about positive and negative roots myself included we can tend to disregard them.
    Last edited by gaelic cowboy; 10-15-2010 at 17:17.
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  5. #5

    Default Re: My stupid math teacher...

    Quote Originally Posted by gaelic cowboy View Post
    There are two solutions to x=y, cowboy, not two answers to sqrt(x).
    Last edited by Tellos Athenaios; 10-15-2010 at 14:47.
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    Senior Member Senior Member gaelic cowboy's Avatar
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    Default Re: My stupid math teacher...

    Quote Originally Posted by Tellos Athenaios View Post
    There are two solutions to x=y, cowboy, not two answers to sqrt(x).
    Indeed at least not yet

    now that I have looked at that sum again I'm beginging to think the X^2 is the wrong part and the first part should read instead

    6 * (X^3) = 36

    cos then

    X^3 = 6

    which is the same as 3 times cubed root of 8
    Last edited by gaelic cowboy; 10-15-2010 at 17:30.
    They slew him with poison afaid to meet him with the steel
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  7. #7
    Future USMC Cobra Pilot Member Prussian to the Iron's Avatar
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    Default Re: My stupid math teacher...

    I would think it was a simple mistake if she hadn't cotinued to argue it. in the 10 minutes spent discussing it, she never once said anything about maybe mistakenly putting the wrong question in, despite my repeated attempts to convince her that it was not possible for both to be true (X^3=6, and 6 X^2=36)

    the way cubed root of 8 came out was because she was factoring....36? I think. either way you do it it comes out as that cannot be right.
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    Member Megas Methuselah's Avatar
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    Default Re: My stupid math teacher...

    Quote Originally Posted by Prussian Iron View Post
    Alright, so on a worksheet today, she worked out a simple math problem. Or so she thought. Upon closer inspection, her answer is completely wrong, in addition to the question not having any sort of non-decimal answer.
    This is not important. The important thing is how hot she is. So, how hot is she?

  9. #9
    Future USMC Cobra Pilot Member Prussian to the Iron's Avatar
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    Default Re: My stupid math teacher...

    Quote Originally Posted by Megas Methuselah View Post
    This is not important. The important thing is how hot she is. So, how hot is she?
    Ugly, short, fat black woman........so a 1 at most. most certainly NOT a TILF.
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    Heaps Gooder Member aimlesswanderer's Avatar
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    Default Re: My stupid math teacher...

    For 3 straight years in HS I had the same crap maths teacher. He would spend the first 5 minutes of class memorising the example in the book, and would then proceed to reproduce the example exactly on the board. Mistakes and all. One year we had a guy who actually had some idea what was going on, and he asked the teacher all manner of questions which he had no idea about.
    "All things are born from darkness, and all things return to darkness". Nausicaa of the Valley of Wind


  11. #11
    Beauty hunter Senior Member Raz's Avatar
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    Default Re: My stupid math teacher...

    Most of the math teachers at my school are annoying at best. One for example, would produce nothing but fear in the class and even in any teacher in proximity, constantly getting neigh on everything wrong, and (via her manipulation and employment of death-stares) manage to prove herself right every time.
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  12. #12
    master of the pwniverse Member Fragony's Avatar
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    Default Re: My stupid math teacher...

    I feel stupid and I'm not even a math-teacher

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