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



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



  • 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?



  • Well, I ended up doing it right to left and forgetting about the minus/plus precedence - then I headdesked.



  • @Charleh said:

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

    Only the imaginary numbers.

     

    PADUM-TISH



  • @Charleh said:

    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.



  • @Master Chief said:

    @Charleh said:

    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.




  • 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.


  • Impossible Mission - B

    @Quango said:

    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.


  • Discourse touched me in a no-no place

    @Quango said:

    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).



  • @Master Chief said:

    *Complains about people not knowing maths.



    *Doesn't know maths.


    THAT is the joke!





  • 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.



  • Minus is right-associative, riiiiiiiiight?



  • 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.



  • @GoatRider said:

    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)



  • 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."


  • Impossible Mission - B

    @too_many_usernames said:

    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...



  • @too_many_usernames said:

    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!

     



  • @joe.edwards said:

    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

     



  • 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



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


  • Impossible Mission - B

    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).



  • @Charleh said:

    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.



  • @pkmnfrk said:

    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!



  • @TGV said:

    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).



  •  It's the 100'000th person.



  • @ekolis said:

    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?



  • @TGV said:

    @pkmnfrk said:

    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 said:

    but the correct answer taking that into account is 5.



  • My guess...

    @pkmnfrk said:

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

    @Charleh said:

    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)


  • Discourse touched me in a no-no place

    @RTapeLoadingError said:

    = 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.



  • @pkmnfrk said:

    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

     

     



  • 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 bring worlds together.




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


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