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Simple fraction Problem

  1. Nov 28, 2016 #1
    Hi,
    I have the following question:
    2 whole number ¼ - 1 whole number 2/3 ------(1)

    1 whole number (1/4 -2/3)

    I am getting –ve sign which is wrong.

    However if I do:

    2 whole number ¼ + 1 whole number 2/3

    Then:

    3whole number (1/4 * 3/3 + 2/3 * 4/4)

    = 3 whole number(3/12 + 8/12)

    = 3 whole number 11/12

    How to solve (1) in the same way as I solved the addition question.

    Zulfi.
     
  2. jcsd
  3. Nov 28, 2016 #2

    PeroK

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    If I had any idea what you are doing I would try to help!
     
  4. Nov 28, 2016 #3

    Mark44

    Staff: Mentor

    ???
    What does this mean?
    What does this mean?
     
  5. Nov 28, 2016 #4

    mfb

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    I moved the thread to our homework section.

    I'm making a guess: you want to calculate ##(2+\frac 1 4) - (1 + \frac 2 3 )##? Then ##(2+\frac 1 4) - (1 + \frac 2 3 ) = 1 + (\frac 1 4 - \frac 2 3)## is a valid step. The last bracket is negative, so what? Further simplification will probably include the "1+" there.
     
  6. Nov 28, 2016 #5
    OKay. I got : 7/12.
    Actually i forgot how i solved it which was giving negative answer. I would reply again.

    Zulfi.
     
  7. Nov 29, 2016 #6

    mfb

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    That answer is correct.
     
  8. Nov 29, 2016 #7
    <<The last bracket is negative, so what?>>
    Hi,
    Thanks. Actually negative sign has significance. Its related to class 4 question. And in class 4 they learn 7-1 but not -7+1 which is -6. So negative has significance. I have to solve it in such a way that I should not get subtraction like : -7 + 1. However 7-1 is allowed. Book has that solution but at this point I don't have access to book.

    Zulfi.
     
  9. Nov 29, 2016 #8

    mfb

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    If coursework subtracts fraction before introducing the concept of negative numbers, something went wrong I think.
     
  10. Dec 1, 2016 #9
    Hi,
    I think its right for class 4 student. Actually they should avoid these questions. I remember studying about subtraction like 7-10 when i started studying algebra in class 6. Okay today i got that book & this is how they did to avoid subraction resulting in -ve numbers:

    3⅓-1¾ = 2 + 1 +⅓-1¾=2+12/12 + 4/12 -1 whole number 9/12 = 1 whole number 7/12

    Hope you would understand my text. Sorry i dont know latex. I typed it in word but cant paste here.
    Actually they subtracted 3-1 which is 2. But they did not perform subtration of larger fraction 3/4 from smaller fraction 1/3 because it would result in a number with negative sign & they did not teach this in class 4.So Instead they added 1 & wrote the larger fraction with minus sign. Then later wrate 12/12 instead of 1 so that all denominators are same.
    This is what i was asking.
    Zulfi.
     
  11. Dec 1, 2016 #10

    mfb

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    I think that arbitrary rule makes calculations more complicated than necessary.

    Another approach would be to convert everthing to x/12.

    (3+1/3) - (1+3/4) = 40/12 - 21/12 = 19/12 = 1 + 7/12

    (This is a readable way to write fractions without LaTeX, by the way)
     
  12. Dec 1, 2016 #11

    Mark44

    Staff: Mentor

    This "whole number" business is very confusing, and was the reason your first post in this thread was so hard to comprehend. A mathematical expression should consist of numbers and operators, not words.
    It would be better to write the above this way:
    3⅓-1¾ = 2 + 1 +⅓-1¾=2+12/12 + 4/12 -1 - 9/12 = (2 - 1) + (16/12 - 9/12) = 1 + 7/12, or ##\frac{19}{12}##.
     
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