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Maths... they do still teach it in schools, right?

Last post 03-08-2013 10:24 AM by blakeyrat. 34 replies.
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  • 03-05-2013 9:05 AM

    Maths... they do still teach it in schools, right?

    I'm on facebook, checking how many awesome friends I have when I see this:

    6 - 1 x 0 + 2 / 2

    ANSWER IT

    "Challenge Accepted" I think to myself. I do mention that it depends on the order of precedence - but the correct answer taking that into account is 5.

    Several thousand people have answered, some of them citing the above 'rules' - but a lot of people are coming to a conclusion of 7

    SEVEN....?

    I asked how anyone had got to 7 and some guy came out with some bullshit about the subtract sign inverting the 1 making it 6 + ((-1 x 0) + (2 / 2))... how exactly the fuck does that work?

    Do I need to go on a bell tower climbing killing spree with a sniper rifle or are people just making this maths shit up on the fly? Tomorrow I expect to walk into a shop, spend £9.35, give the cashier £10 and get 7p change because they just decided to add some their own bullshit rules or maybe they are just counting in base 11.5...

    Then I realise its 7 :D

    Get to da CHOPPAAAAA
  • 03-05-2013 9:09 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    The minus sign doesn't matter. 6 + 0 is the same as 6 - 0.

    This is a signature. It's not a good one, but it's still a signature.


  • Mon, February 30 2010 2:64 PM

    • Fabulous Darth Vader
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    • In a Glittery galaxy far, far away
    • Posts π x 10-14


    I have cornified this post, pray I don't cornify it further.






  • Filed under:
  • 03-05-2013 9:10 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    BEDMAS:

    1. Brackets
    2. Exponents
    3. Division, Multiplication
    4. Addition, Subtraction

    = 6 - 1 x 0 + 2 / 2

    = 6 - (1 x 0) + (2 / 2)

    = 6 - (0) + (1)

    = 6 + 1

    = 7

    Where did 5 come from?

  • 03-05-2013 9:13 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Well, I ended up doing it right to left and forgetting about the minus/plus precedence - then I headdesked.
    Get to da CHOPPAAAAA
  • 03-05-2013 9:21 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Charleh:
    or are people just making this maths shit up on the fly?
     

    Only the imaginary numbers.

     

    PADUM-TISH


    In complex analysis, a meromorphic function on an open subset D of the complex plane is a function that is holomorphic on all D except a set of isolated points

    Filed under:
  • 03-05-2013 9:27 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Charleh:

    I'm on facebook, checking how many awesome friends I have when I see this:

    6 - 1 x 0 + 2 / 2

    ANSWER IT

    "Challenge Accepted" I think to myself. I do mention that it depends on the order of precedence - but the correct answer taking that into account is 5.

    Several thousand people have answered, some of them citing the above 'rules' - but a lot of people are coming to a conclusion of 7

    SEVEN....?

    I asked how anyone had got to 7 and some guy came out with some bullshit about the subtract sign inverting the 1 making it 6 + ((-1 x 0) + (2 / 2))... how exactly the fuck does that work?

    Do I need to go on a bell tower climbing killing spree with a sniper rifle or are people just making this maths shit up on the fly? Tomorrow I expect to walk into a shop, spend £9.35, give the cashier £10 and get 7p change because they just decided to add some their own bullshit rules or maybe they are just counting in base 11.5...

    Then I realise its 7 :D

    *Complains about people not knowing maths.

    *Doesn't know maths.
    All the technology and software in the universe is just as useless when the end user has the IQ of a sack of hammers.
    - Me
  • 03-05-2013 9:48 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Master Chief:
    Charleh:

    I'm on facebook, checking how many awesome friends I have when I see this:

    6 - 1 x 0 + 2 / 2

    ANSWER IT

    "Challenge Accepted" I think to myself. I do mention that it depends on the order of precedence - but the correct answer taking that into account is 5.

    Several thousand people have answered, some of them citing the above 'rules' - but a lot of people are coming to a conclusion of 7

    SEVEN....?

    I asked how anyone had got to 7 and some guy came out with some bullshit about the subtract sign inverting the 1 making it 6 + ((-1 x 0) + (2 / 2))... how exactly the fuck does that work?

    Do I need to go on a bell tower climbing killing spree with a sniper rifle or are people just making this maths shit up on the fly? Tomorrow I expect to walk into a shop, spend £9.35, give the cashier £10 and get 7p change because they just decided to add some their own bullshit rules or maybe they are just counting in base 11.5...

    Then I realise its 7 :D

    *Complains about people not knowing maths.

    *Doesn't know maths.
  • 03-05-2013 9:53 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    BODMAS, as my maths teacher used to say.. [B]rackets (parantheses, actually, but it sounds better than PODMAS) [O]f (aka "multiply") [D]ivision M]ultiplication [A]ddition [S]ubtraction Put into any spreadsheet and that's the answer.
    -= Quango =-
  • 03-05-2013 10:00 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Quango:
    BODMAS, as my maths teacher used to say.. [B]rackets (parantheses, actually, but it sounds better than PODMAS) [O]f (aka "multiply") [D]ivision M]ultiplication [A]ddition [S]ubtraction Put into any spreadsheet and that's the answer.
    PEMDAS in these parts. Parentheses, exponents, multiplication/division, addition/subtraction. I swear my sixth grade teacher turned it into a song that we had to sing for a grade.
    Signatures are stupid.
  • 03-05-2013 10:30 AM In reply to

    • PJH
    • Top 10 Contributor
    • Joined on 02-14-2007
    • Newcastle, UK
    • Posts 3,906

    Re: Maths... they do still teach it in schools, right?

    Quango:
    BODMAS, as my maths teacher used to say..

    [B]rackets (parantheses, actually, but it sounds better than PODMAS)
    [O]f (aka "multiply")
    [D]ivision
    M]ultiplication
    [A]ddition
    [S]ubtraction

    Put into any spreadsheet and that's the answer.
    Your Maths teacher was somewhat incorrect; or you're misremembering - the O stands for Orders (exponents and roots).
    "Because you watched 'The Very Hungry Caterpillar,' we recommend 'The Human Centipede.'"
    --
    UED - Countryside: To kill Piers Morgan
  • Parp!
  • 03-05-2013 10:47 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Master Chief:
    *Complains about people not knowing maths.

    *Doesn't know maths.

    THAT is the joke!
      <-  I couldn't make my shit work, so here's a Godzilla head.
  • 03-05-2013 11:09 AM In reply to

    Re: Maths... they do still teach it in schools, right?

  • 03-05-2013 12:02 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    Fucking Maths: How do They Work? Every time I start thinking that the posters to TDWTF or slashdot are freaking boneheads, I just go over and read a couple Facebook or Yahoo threads. Then I realize what true microcraniality is.
  • 03-05-2013 12:30 PM In reply to

    • Ben L.
    • Top 10 Contributor
    • Joined on 12-22-2010
    • Inventor of the 186-hour work week
    • Posts 3,607

    Re: Maths... they do still teach it in schools, right?

    Minus is right-associative, riiiiiiiiight?
  • Morbs is the smartest!
  • 03-05-2013 4:52 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    Don't feed the trolls. It's deliberately intended to be ambiguous, so you'll comment on it. They are trolling for comments and likes. Accounts with a lot of comments and likes are valuable to advertisers.
  • 03-05-2013 5:28 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    GoatRider:
    Don't feed the trolls. It's deliberately intended to be ambiguous, so you'll comment on it. They are trolling for comments and likes. Accounts with a lot of comments and likes are valuable to advertisers.
     

    What? No it's not, it's perfectly clear.

    This one is deliberately ambiguous: a/b(c+d)

    Because written as a/b*(c+d) the left to right rule gives this order of evaluation: (a/b)*(c+d).
    But the ommited multiplication sign creates ambiguity because that's usually only done in situations where you would have this order of evaluation: a/(b*(c+d)), the same way as writing it out as a fraction gives you implicit parentheses:

           a

    -------------

     b*(c+d)

  • 03-06-2013 4:53 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    I was just reading the Excel woes sheet - and it kind of crosses with this thread:

    Type this into Excel and be angry:

    Cell A1: =-5

    Cell A2: =-a1^2+1

    Cell A3: =+1-a1^2

    You can actually find the history behind this !!fun!! with a search, but it's still irritating.  I don't know how many spreadsheets have given me funny results because of this "design choice."

  • 03-06-2013 5:00 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    too_many_usernames:

    I was just reading the Excel woes sheet - and it kind of crosses with this thread:

    Type this into Excel and be angry:

    Cell A1: =-5

    Cell A2: =-a1^2+1

    Cell A3: =+1-a1^2

    You can actually find the history behind this !!fun!! with a search, but it's still irritating.  I don't know how many spreadsheets have given me funny results because of this "design choice."

    Am I missing something?

    -a1^2+1 = 5^2+1 = 25 + 1 = 26

    +1-a1^2 = +1 - (-5)^2 = +1 - 25 = -24

    Which is exactly the result I get from Excel...

    Signatures are stupid.
  • 03-06-2013 5:59 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    too_many_usernames:

    Cell A1: =-5

    Cell A2: =-a1^2+1

    Cell A3: =+1-a1^2

     

    A2 has the value of (-5) raised to the second power, with one added to the result.  

    Do you want it to have the value of (-5) raised to the third power?  If so, you need parentheses!

     

  • 03-06-2013 6:22 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    joe.edwards:

    Am I missing something?

    -a1^2+1 = 5^2+1 = 25 + 1 = 26

    +1-a1^2 = +1 - (-5)^2 = +1 - 25 = -24

     Which is exactly the result I get from Excel...

    The question is on the precedence on the - sign in front of the A1. Either you write

    -a1^2+1 = -(-5)^2+1 = 25 + 1 = -24

    +1-a1^2 = +1 - (-5)^2 = +1 - 25 = -24
    or by using the rule that "-A1" is exactly the same as "+ ( -1 * A1 ):

    -a1^2+1 = (-1 * -5)^2+1 = 25 + 1 = 26

    +1-a1^2 = +1 + (-1 * -5)^2 = +1 - 25 = 26
    The second one, giving 26, seems wrong. Taking the power of 2 of A1 should have precedence over applying the minus sign

     

    It's... Monkey Piston's Frying Circle!
  • 03-06-2013 6:23 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    I think the point is that the minus sign in A2 is being treated differently than in A3. Eg, in A2, it has higher priority than the exponent:

    =(-a1)^2+1

    Instead of

    =-(a1^2)+1

    Whereas in A3, the minus sign is the subtraction operator, and has a lower priority than the exponent. If you rewrite A2 like this, it matches A3:

    =0-a1^2+1

    I guess they added logic to handle minus signs in places where subtraction doesn't make sense, like the beginning of the formula, or this:

    =5 +- a1

  • 03-06-2013 6:35 PM In reply to

    • ekolis
    • Top 100 Contributor
    • Joined on 01-09-2008
    • Cincinnati, OH, USA
    • Posts 600

    Re: Maths... they do still teach it in schools, right?

    TRWTF is British English. If it's really "maths", it should be "they do still teach THEM in schools, right?"
    I'm Spark Mandrill, and I'll... hey... can I... what, it BOUNCES?... 'kay, I'm splodin' now.
  • 03-07-2013 12:29 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    I guess I see it that - can be a unary operator or a binary operator, and that as a unary operator it yields the additive inverse of the number and has immediate precedence, while as a binary operator it has lesser precedence. In any case, it's acting in line with my expectations. -x is evaluated as (-1x).
    Signatures are stupid.
  • 03-07-2013 3:22 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Charleh:
    Well, I ended up doing it right to left and forgetting about the minus/plus precedence - then I headdesked.
    In that case you should get 1, not 5.
    You'll probably find that the forum experience is improved by going to the "Site Options" tab of "Edit Profile" and turning off "Display User Signatures".
  • 03-07-2013 7:50 AM In reply to

    • TGV
    • Top 75 Contributor
    • Joined on 10-09-2005
    • Posts 704

    Re: Maths... they do still teach it in schools, right?

    pkmnfrk:

    BEDMAS:

    1. Brackets
    2. Exponents
    3. Division, Multiplication
    4. Addition, Subtraction

    = 6 - 1 x 0 + 2 / 2

    = 6 - (1 x 0) + (2 / 2)

    = 6 - (0) + (1)

    = 6 + 1

    = 7

    Where did 5 come from?

     

    Congratulations. You are the 100,000 person who didn't read the whole story. You have won an Internet!

  • 03-07-2013 8:48 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    TGV:
    Congratulations. You are the 100,000 person who didn't read the whole story. You have won an Internet!
     

    Is that the one-hundred thousandth person, or the one hundredth to a precision of one thousandth?

     

     

     

    (Yes, this is intentional).

  • 03-07-2013 8:59 AM In reply to

    Re: Maths... they do still teach it in schools, right?

     It's the 100'000th person.


    In complex analysis, a meromorphic function on an open subset D of the complex plane is a function that is holomorphic on all D except a set of isolated points

    Filed under:
  • 03-07-2013 1:44 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    ekolis:
    TRWTF is British English. If it's really "maths", it should be "they do still teach THEM in schools, right?"
    And if it's British English, right? should be innit?

  • 03-07-2013 3:35 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    TGV:

    pkmnfrk:

    BEDMAS:

    1. Brackets
    2. Exponents
    3. Division, Multiplication
    4. Addition, Subtraction

    = 6 - 1 x 0 + 2 / 2

    = 6 - (1 x 0) + (2 / 2)

    = 6 - (0) + (1)

    = 6 + 1

    = 7

    Where did 5 come from?

     

    Congratulations. You are the 100,000 person who didn't read the whole story. You have won an Internet!

    I was calling into attention a bit of the story that you clearly did not read:

    Charleh:
    but the correct answer taking that into account is 5.
  • 03-07-2013 7:01 PM In reply to

    Re: Maths... they do still teach it in schools, right?

    My guess...

    pkmnfrk:

    I was calling into attention a bit of the story that you clearly did not read:

    Charleh:
    but the correct answer taking that into account is 5.

    = 6 - 1 x 0 + 2 / 2

    = 6 - (1 x 0) + (2 / 2)

    = 6 - (0 + 1)

    Certified Internet Engineer (CIE)

  • 03-08-2013 4:18 AM In reply to

    • PJH
    • Top 10 Contributor
    • Joined on 02-14-2007
    • Newcastle, UK
    • Posts 3,906

    Re: Maths... they do still teach it in schools, right?

    RTapeLoadingError:

    = 6 - (1 x 0) + (2 / 2)

    = 6 - (0 + 1)

    But clearly wrong, because those two aren't equivalent, since you're introducing a multiplication in the second one.
    "Because you watched 'The Very Hungry Caterpillar,' we recommend 'The Human Centipede.'"
    --
    UED - Countryside: To kill Piers Morgan
  • Parp!
  • 03-08-2013 4:41 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    pkmnfrk:

    BEDMAS:

    1. Brackets
    2. Exponents
    3. Division, Multiplication
    4. Addition, Subtraction

    = 6 - 1 x 0 + 2 / 2

    = 6 - (1 x 0) + (2 / 2)

    = 6 - (0) + (1)

    = 6 + 1

    = 7

    Where did 5 come from?

    5 comes from inserting an invisible parentheses that don't belong, opening either before the 1 or the 0 and ending at the end of the statement.

    Solving in reverse-polish notation you get:

    6 (push), 1 (push), 0 (push),  (multiply), (subtract), 2 (push), 2 (push), (divide), (add)

    Each operation either pushes a number onto the stack or performs a binary operation between the 2 most recent numbers on the stack.

    A subtract subtracts the current value from the one before it on the stack.

    An operation replaces the last 2 numbers on the stack with the value of the current one.

    Stack looks like this:

    (push 6) 6

    (push 1) 6, 1

    (push 0) 6, 1, 0

    (multiply) 6, 0

    (subtract) 6

    (push 2 ) 6, 2

    (push 2) 6, 2, 2

    (divide) 6, 1

    (add) 7

     

     

  • 03-08-2013 9:45 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    Mr CButtius! Will the test be graded on a curve? I did bad on the quiz because my dog was barking and kept me up but I need a C on the test or I won't be able to go to prom!!!

    God you people are boring.

      <-  I couldn't make my shit work, so here's a Godzilla head.
  • 03-08-2013 9:58 AM In reply to

    Re: Maths... they do still teach it in schools, right?

     I bring worlds together.



    In complex analysis, a meromorphic function on an open subset D of the complex plane is a function that is holomorphic on all D except a set of isolated points

    Filed under: ,
  • 03-08-2013 10:24 AM In reply to

    Re: Maths... they do still teach it in schools, right?

    There, now I got SOME enjoyment out of this thread.

      <-  I couldn't make my shit work, so here's a Godzilla head.
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