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Math Help - Fractions

  1. #1
    Member GAdams's Avatar
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    Fractions

    Can anybody give me give me some idea how to tackle this:

    1/ (2/5) - 1/ (2/3)
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by GAdams View Post
    Can anybody give me give me some idea how to tackle this:

    1/ (2/5) - 1/ (2/3)
    is this \frac 1{\frac 25} - \frac 1{ \frac 23}?

    if so, for starters, you can flip both fractions to get: \frac 52 - \frac 32

    now can you continue?
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  3. #3
    Member GAdams's Avatar
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    Quote Originally Posted by Jhevon View Post
    is this \frac 1{\frac 25} - \frac 1{ \frac 23}?

    if so, for starters, you can flip both fractions to get: \frac 52 - \frac 32

    now can you continue?
    Fraid not. A bit more please...
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  4. #4
    Math Engineering Student
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    When you have an expression like

    x=\frac a{\dfrac bc}

    it's the same if we say x=a:\dfrac bc

    Does that make sense?
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  5. #5
    Member GAdams's Avatar
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    OK. These are completely new to me but here goes:

    1/ (2/5) - 1/ (2/3)

    = 1 : 2/5 - 1: 2/3

    1/1 divide by 2/5 flip to get 1/1 multiply 5/2

    1/1 divide by 2/3 flip to get 1/1 multiply 3/2

    5/2 - 3/2 = 2/2 = 1

    I have a feeling this is totally wrong....
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  6. #6
    Math Engineering Student
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    It is correct!

    Trust in your answers, if you apply correctly the learnt, there's nothing to worry about.
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  7. #7
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by GAdams View Post
    OK. These are completely new to me but here goes:

    1/ (2/5) - 1/ (2/3)

    = 1 : 2/5 - 1: 2/3

    1/1 divide by 2/5 flip to get 1/1 multiply 5/2

    1/1 divide by 2/3 flip to get 1/1 multiply 3/2

    5/2 - 3/2 = 2/2 = 1

    I have a feeling this is totally wrong....
    There is a way to avoid the ":" stuff. Consider the fraction:
    \frac{1}{\frac{2}{5}}

    We need to remove the fraction in the denominator of the "overall" fraction. How would you do this? Well, note that if we multiply \frac{2}{5} by 5 the result is an integer: 2. But what we multiply in the denominator we must also multiply in the numerator. So:
    \frac{1}{\frac{2}{5}} = \frac{1}{\frac{2}{5}} \cdot \frac{5}{5} = \frac{1 \cdot 5}{\frac{2}{5} \cdot 5} = \frac{5}{2}

    (No offense Krizalid. I hate ratio notation with a passion. )

    -Dan
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  8. #8
    Math Engineering Student
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    Doesn't matter.

    If it's necessary, I try to explain pedagogically so that the user understands the problem well.
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