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Thread: O/T: Math. Again (I am trying to learn) :)

  1. #1
    Join Date
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    Default O/T: Math. Again (I am trying to learn) :)

    So it seems I like to work heavy math problems from the end to beginning, backwards.

    No, I dont want the answer. But it is easier for me to solve the problem from right to left.

    I think I made a multiplication system that also worked backwards.

    Say
    235,975
    X
    24,763

    And no thank you, I dont do that stuff anymore I am retired


    Answer in moments with a pencil and paper. Work the math backwards. Get rid of the heavy stuff and pare down the small numbers.

    I thought that is how everyone did long number math. JR

    UGG trade mark lol
    Last edited by JRouche; 07-20-2019 at 02:39 AM.
    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  2. #2
    Join Date
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    I'm not sure what you mean. Multiplication of numbers like you show is performed by going right to left on the multiplicand, and subtotals left-shifted for each power of 10 in the digits of the multiplier. It's probably a good mental exercise to perform such operations by hand, occasionally, but it is rarely needed when you can buy a calculator for less than the cup of coffee you will need to lubricate your brain for manual math.

    If you really want to dig deep into the mathematical and computation gymnastics involved in computer programming, read the following:

    https://docs.oracle.com/cd/E19957-01..._goldberg.html

    For example:
    Another grey area concerns the interpretation of parentheses. Due to roundoff errors, the associative laws of algebra do not necessarily hold for floating-point numbers. For example, the expression (x+y)+z has a totally different answer than x+(y+z) when x = 1030, y = -1030 and z = 1 (it is 1 in the former case, 0 in the latter).
    There are some shortcuts that can be used sometimes for long number math. For instance:

    1,234 x 99 can be simplified as 1,234 X 100 -1,234 = 123,400 - 1,234 = 122,166

  3. #3
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    Is it just me? ...or is there a shortage of coherence in this room?

  4. #4
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    Perhaps. But I got zig-zags and quit reading.

  5. #5
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    The most interesting math I find is geometry and trig in the application of what we do, and throw in some calculus for PID algorithms in motion control. Everything else will bore you to tears.

    Sent from my SM-G950U1 using Tapatalk

  6. #6
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    I could never figure out the deal of 'multiplication before everything else' deal. Where you have a string of math equations and somewhere in the middle is a multiplication equation.

    Like:

    4+5-3/2+5x7-6=

    I have it engraved in my head to just work from left to right. But I read you are supposed to start with the multiplication first?
    Andy

  7. #7
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    Jun 2016
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    Quote Originally Posted by lynnl View Post
    Is there a shortage of coherence in this room?
    No, but there seems to be a shortage of coherence.

  8. #8
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    Default

    Quote Originally Posted by vpt View Post
    I could never figure out the deal of 'multiplication before everything else' deal. Where you have a string of math equations and somewhere in the middle is a multiplication equation.

    Like:

    4+5-3/2+5x7-6=

    I have it engraved in my head to just work from left to right. But I read you are supposed to start with the multiplication first?
    4+3*2 = 10

    4+3*2 does not equal 7*2 = 14 [ if the desired value was 14 then it would have to be written (4+3)*2 ]

    Actually, the rule is;

    do what's inside the parentheses first
    then
    exponentiation
    multiplication/division
    addition/subtraction
    Regards, Marv

    Home Shop Freeware - Tools for People Who Build Things
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  9. #9
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    Don't remember when I first learned the mnemonic: "My Dear Aunt Sally" - Multiply, Divide, Add, Subtract (i.e. the order of operations). But it was probably before they muddied the water with that exponentiation stuff.

    Like Marv's example above shows, it kinda helps to have some sort of agreed upon way of doing things.
    Last edited by lynnl; 07-20-2019 at 12:27 PM.

  10. #10
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    Khan academy is a wonderful thing. I need to get back into it to exercise my brain. Also watching the video on YouTube of a guy building a simple video card on a breadboard to drive a VGA monitor using logic chips and an eeprom was a life altering experience, "so THAT'S how those analog things are used!"

    Sent from my SM-G950U1 using Tapatalk

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