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Math Help - Bodmas Confusion

  1. #1
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    Bodmas Confusion

    Hello Everyone,

    I have searched the forums and can't seem to find an answer which satisfies my question. I hope this dosen't irritate anyone as it is a very basic question.

    I have been fiddling around with some bodmas questions and have hit a brick wall, I can get the correct answer however the final bit of the process is confusing me and I want to understand it rather than "just know it works".

    Below is my problem.

    12 + 9 - 18 + 4 -15 + 6 -8

    = (12+9) + (4+6) - (18 - 15) - 8

    = 21+10) - (18+15) + 8 < This is the part I am confused about

    = 31 - 41 = -10

    Why does it change from (18-15) - 8 to (18+15) + 8. It must have something to do with their being two minus but I thought the two negatives make a positive rule only worked with negative numbers.

    Thanks in advance.
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by tkdvipers View Post
    Hello Everyone,

    I have searched the forums and can't seem to find an answer which satisfies my question. I hope this dosen't irritate anyone as it is a very basic question.

    I have been fiddling around with some bodmas questions and have hit a brick wall, I can get the correct answer however the final bit of the process is confusing me and I want to understand it rather than "just know it works".

    Below is my problem.

    12 + 9 - 18 + 4 -15 + 6 -8

    = (12+9) + (4+6) - (18 - 15) - 8 <===This should be (12+9)+(4+6)-(18+15)-8. Remember, the 18 and 15 are both negative, so when you group them you must precede the group with a negative sign and change both their signs within the group.

    = (21+10) - (18+15) + 8 < This is the part I am confused about Should be -8

    = 31 - 41 = -10

    Why does it change from (18-15) - 8 to (18+15) + 8. It must have something to do with their being two minus but I thought the two negatives make a positive rule only worked with negative numbers.

    Thanks in advance.
    Corrections in red
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  3. #3
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    Joined
    Aug 2008
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    Thanks so much.

    The book I am learning from does not make it very clear. You have cured my confusion.

    Thank you
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