Page 4 of 4 FirstFirst 1234
Results 28 to 33 of 33

Thread: Attention mathematicians: Help

  1. #28

    Default Re: Attention mathematicians: Help

    I had a ladie teacher in math, algebra, and geometry who stood, 6'3" and weighed around 115#. I knew what 38-24-36 meant.

  2. #29

    Default Re: Attention mathematicians: Help

    A colleague with a doctorate in mathematics from the University of Minnesota answered 2 while my teenage daughter (a real poindexster though) came up with 288. My colleague quickly backpedaled and changed the subject.

    Maybe psychologists/psychiatrists could use the equation as a tool to interpret personalities.

  3. #30

    Default Re: Attention mathematicians: Help

    I hadn't realized that this was some type of internet rage until I saw the video. Just a bit ridiculous and highly irritating.

    But, for the mathmaticians out there, is there a name for the two types of displays [grouped under numbers 1.) and 2.)] that have been shown in this thread:

    1.)
    48
    --- (9+3) = 288, or
    2

    48 (9+3)
    -------- = 288
    2

    as opposed to,

    48
    ---------- = 2
    2 (9+3)


    and,


    2.)

    48/2(9+3) = 288

    as opposed to,

    48/(2(9+3)) = 2 ---[borrowing oldfart's thoughtful answer to my question]


    I ask because I figure mathematicians like to have a name for everything.

    Also, is there a name given to the procedure for converting an equation as expressed under 1.) to an equation as expressed under 2). And vice versa.

    Notice that the procedure for converting the expressions under the "as opposed to" phrases, apparently, calls for the addition of parentheses (or the subtraction of parentheses in the case of reversing the procedure).

    However, also notice that, during the conversion from the third equation under 1.) to the second equation under 2.), the addition of parentheses is MANDATORY (seemingly), whereas during the reverse procedure, converting from the second equation under 2.) to the third equation under 1)., it would appear that the elimination of that set of parentheses is OPTIONAL.

    Is this particular process codified and does it have a name?
    Last edited by LkwdSteve; 06-26-2011 at 02:01 PM. Reason: screwed up the second to last paragraph and had to correct
    DSCH: a Soviet artist's reply to unjust criticism.

  4. #31

    Default Re: Attention mathematicians: Help

    Steve, good question. I don't have enough background in mathematics to answer if there is a specific name.

    -----------

    I really didn't want to argue for one answer or the other but can't resist offering an opinion. I believe the answer is 288 because one must execute the calculation applying the define mathematical rules based on exactly how the equation is written.

    48/2(9+3) cannot be assumed to be 48/[2(9+3)] for precisely the same reasoning one cannot assume the writer meant 48/[2(9+3)] to be 48/2(9+3). They both have distinctly different results.

    Select *
    from fileName
    where field1 = 'A' and field2 = 'B' or field3 = 'C'

    will have a different result set than

    Select *
    from fileName
    where field1 = 'A' and (field2 = 'B' or field3 = 'C').

    Operands (with their order of operation) have rules and the calcs must be performed in strict compliance. If one is expecting a result set that needs parens then the equation must be written with them. If the parens are omitted then we must perform the calculation assuming they were intended NOT to be included.

    /end rant

    Edit: If anyone is actually interested in reading about the application of set theory I recommend Joe Celko's books SQL for Smarties and Thinking in Sets.
    Last edited by pm01; 06-26-2011 at 07:50 PM.

  5. #32

    Default Re: Attention mathematicians: Help

    I think it has been clearly established that the answer is supposed to be 288.

    It's a bad example of this type of problem. In other words, better examples can be choosen to illustrate the "issue".

    Consider:

    Let a=2


    I would automatically figure 4/2a = 1

    Yet, I would be wrong, wouldn't I?

    According to the established convention,

    4/2(a) = 4, but so too would 4/2a = 4. Yesterday I would have AUTOMATICALLY calculated both answers to be 1.

    I guess I just HAVE TO KNOW that, if I wish to have a divisor consisting of a number multiplied by an unknown, that entire divisor must be encased in parentheses, when using this "keypad" as opposed to "longhand" method of display. This, of course, is not true of the dividend*.

    Thus, 4/(2a) = 1, or 4/[2(a)] = 1.

    Plus we get the, on the surface, "weird" situation where 4a/2 = 4/2a*, with both equaling 4, given a = 2. To me, the situation cries for the 4/2 to be encased in it's own parentheses, ie (4/2)a = 4, which is how I would write it by keypad, even though PEDMAS tells me the situation is crystal clear without my adding symbols.



    I NEVER recall this being an issue when I was in school. Perhaps that's because, back then, everything was mostly "longhand", though to be sure, we all had learned three ways to write division,---, /, and 2 dots centered one above and one below a straight line (that symbol isn't on my keyboard).


    *Note that in the expression 4a/2, it doesn't matter whether you first divide the a by 2 or first multiply the a times 4. Your intention during the solving process can be for multiplication to occur in the dividend and that product then divided. But unless you place the 4a into parentheses, ie (4a), division will happen first (unless pm01 is correct about arrival sequence). The a will be divided by 2 and then that quotient will be multiplied by 4. But you get the same answer either way.
    Last edited by LkwdSteve; 06-26-2011 at 11:23 PM. Reason: to add a note at bottom
    DSCH: a Soviet artist's reply to unjust criticism.

  6. #33
    Olympic Champ RYou's Avatar
    Join Date
    Mar 2007
    Location
    New Jersey
    Posts
    8,376

    Default Re: Attention mathematicians: Help

    48/2(9+3)

    Work within (...) always takes priority (9+3) = (12)

    48/2(12)

    2(12) infers multiplication, because there is no x or *, the work to the right of the divisor takes priority .....24

    48/24 = 2

    Had an x or * been included 48/2*(9+3), then the equation would follow the order of operation 48 / 2 * 12 = 288

    PS, simple algebra, not physics
    Life's not the breaths you take, the breathing in and out that gets you through the day ain't what it's all about. It's the moments that take your breath away.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •