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Homework Help: BIDMAS Evaluating Expression Without Calculator

  1. Oct 14, 2017 #1
    Hi there,

    I'm hoping somebody can help me. I have to evaluate the following expression using BIDMAS rules without using a calculator: 1-2/32

    I can get as far as 1-2/9 but the answer is 7/9. I don't understand how to get from 1-2/9 to 7/9 in my head. For instance 2/9 = 0.2 recurring, but 1-0.22222222222 etc doesn't give me 7/9.

    Help me! :)
     
  2. jcsd
  3. Oct 14, 2017 #2

    mfb

    User Avatar
    2017 Award

    Staff: Mentor

    I moved your thread to our homework section.

    You can express 1 as 9/9, that makes it easier to subtract 2/9.

    In general, if you want to add/subtract with fractions, make sure everything has the same denominator.
     
  4. Oct 14, 2017 #3
    That is perfect - thank you so much! I didn't even think of that! :)
     
  5. Oct 14, 2017 #4

    Mark44

    Staff: Mentor

    Sure it does.
    1 - 0.222... (recurring infinitely far) = 0.777... (recurring infinitely far) = 7/9
     
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