Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    16
    ReputationRep:
    Sorry if this has been mentioned before, but surely they wouldn't give the same answer? According to PEMDAS, multiplication comes before division and BODMAS states the other way.

    So for  6 \div 2 \times 5

    Using PEMDAS gives us 0.6
    Using BODMAS gives us 15

    Any opinions on this?
    Offline

    0
    ReputationRep:
    Both.
    Offline

    16
    ReputationRep:
    (Original post by InadequateJusticex)

    Any opinions on this?
    Multiplication and division are the same operation and are, therefore, completed left to right

    So the answer is 15
    Offline

    0
    ReputationRep:
    What's PEDMAS? Wow everything changes when you leave school

    Oh I spelt it wrong. It's PEMDAS
    • Thread Starter
    Offline

    16
    ReputationRep:
    (Original post by Cephalus)
    What's PEDMAS? Wow everything changes when you leave school
    The american version of BODMAS
    • PS Helper
    Offline

    14
    PS Helper
    (Original post by InadequateJusticex)
    Sorry if this has been mentioned before, but surely they wouldn't give the same answer? According to PEMDAS, multiplication comes before division and BODMAS states the other way.

    So for  6 \div 2 \times 5

    Using PEMDAS gives us 0.6
    Using BODMAS gives us 15

    Any opinions on this?
    Strictly speaking, this isn't resolved by BODMAS/PEMDAS. These rules give division and multiplication equal priority, and likewise addition and subtraction: after all, division is just multiplication by a fraction, and subtraction is just addition of a negative. So in this sense, BODMAS, BOMDAS, BODMSA and BOMDSA all give the same rule.

    If you interpret 6 \div 2 \times 5 to be just a sequence of operations to carry out then by default you should work from left to right, to obtain 15.

    But in the strictest sense, this is ambiguous. There are 'hidden brackets', which make it either (6 \div 2) \times 5 or 6 \div (2 \times 5), the former giving 15 and the latter giving 0.6, and without further context it's impossible to say with confidence which it is. In order to disambiguate, brackets should be added, or the fraction should be written in vertical notation to give either \dfrac{6}{2} \times 5 or \dfrac{6}{2 \times 5}.
    Offline

    18
    ReputationRep:
    (Original post by InadequateJusticex)
    Sorry if this has been mentioned before, but surely they wouldn't give the same answer? According to PEMDAS, multiplication comes before division and BODMAS states the other way.

    So for  6 \div 2 \times 5

    Using PEMDAS gives us 0.6
    Using BODMAS gives us 15

    Any opinions on this?
    Multiplication & Division are equivalent so saying one comes before the other makes little sense. Why not reduce it down to a product? 6 \div 2 \times 5=6 \times \dfrac{1}{2} \times 5=15
    • PS Helper
    Offline

    14
    PS Helper
    (Original post by Lord of the Flies)
    Multiplication & Division are equivalent so saying one comes before the other makes little sense. Why not reduce it down to a product? 6 \div 2 \times 5=6 \times \dfrac{1}{2} \times 5=15
    The real issue is in deciding whether

    (i): 6 \div 2 \times 5 = 6 \times \dfrac{1}{2} \times 5

    or

    (ii): 6 \div 2 \times 5 = 6 \times \dfrac{1}{2 \times 5}

    I'd expect (i) is the most common, and certainly what you'd assume if you were doing a basic (say, pre-A-level) arithmetic without any context to it; but there's no universally accepted reason why the notation couldn't also refer to (ii).
    Offline

    18
    ReputationRep:
    (Original post by nuodai)
    there's no universally accepted reason why the notation couldn't also refer to (ii).
    Ah, I wasn't aware. I thought "separating" the operations and substituting with their equivalents made complete sense given the absence of brackets:

     (+6)\;(\div 2)\;(\times 5)=(+6)\;(\times 1/2)\;(\times 5)

    Strange that there is still no universally accepted method for these things!
    Offline

    0
    ReputationRep:
    (Original post by Lord of the Flies)
    Ah, I wasn't aware. I thought "separating" the operations and substituting with their equivalents made complete sense given the absence of brackets:

     (+6)\;(\div 2)\;(\times 5)=(+6)\;(\times 1/2)\;(\times 5)

    Strange that there is still no universally accepted method for these things!
    Mhm, there's a facebook question homogeneous to this, and in fact, it's both. Maybe they'll eventually overhaul the problem by just stating that in these scenarios a "left-to-right" approach is the more suitable.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you rather give up salt or pepper?
    Useful resources

    Make your revision easier

    Maths

    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here

    Equations

    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Write a reply...
    Reply
    Hide
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.