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Math Help - Dbl checking answer with Reasoning rational or irrational.

  1. #1
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    [Solved]Dbl checking answer with Reasoning rational or irrational.

    ================================================== ========
    Question (1)
    ================================================== ========
    Area of circle= A

    Area=╥R

    Radius = 1/√╥

    A=╥(1/√╥)

    =╥ * 1/╥

    A= ╥

    Correction

    A=╥(1/√╥)

    =╥ * 1/╥
    =1


    Therefore rational because can be express as a fraction.

    Correction
    Therefore it is rational because 1 can be express as 1/1 where both numerator and denominator is an integer.

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    Question 2
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    Find side length of Square.

    Let side length of square =S
    Given only diagonal length = √72 cm

    (√72)=2S
    72=2S
    72/2=S
    36=S
    √36=S
    6=S

    Therefore rational because can be express as a fraction.

    Correction
    Therefore it is rational because 6 can be express as 6/1 where both numerator and denominator is an integer.

    ================================================== ========

    I have been prompted to provide reasons besides stating rational or irrational.
    May i know is the above correct ? Especially Question 2 because i suspect that my answer might be wrong.
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    Last edited by vincor; October 13th 2011 at 01:23 AM. Reason: Solved
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  2. #2
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    Re: Dbl checking answer with Reasoning rational or irrational.

    1) your answer for A is wrong (re-check the last step....what should \pi(1/\pi) be?)

    2) your answer here is correct, but:

    you need to be a little more precise about what a "fraction" is.

    1/√2 looks like a fraction, but it isn't rational.

    a number is rational if (and only if) it can be written as a fraction a/b WHERE

    (and this is kind of important), b is not 0, and both a and b are INTEGERS.

    so for 2), 6 is rational, because....6 = 6/1, 1 is not 0, and both 1 and 6 are integers.
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  3. #3
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    Re: Dbl checking answer with Reasoning rational or irrational.

    Correction altered in red.
    Is that correct ?

    I've been haunted by IGCSE's reasoning part because i had poor explaination and been googling around for answers because i had no idea what answer would be most appropriate . Though mostly been formulas. I had also followed chapters on Cambridge's IGCSE and it came with answers only and no solution.
    So i thought of trying here and thanks alot.
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  4. #4
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    Re: Dbl checking answer with Reasoning rational or irrational.

    the denominator has to be non-zero, as well. although this is pretty obvious here, it's less obvious when you are just dealing with symbols.
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  5. #5
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    Re: Dbl checking answer with Reasoning rational or irrational.

    Thx for the help. I guess i'll stick with your reasoning part because it's the exact form that's required. After googling around i notice that most tends to add in in conjunction with this rule.
    Rational numbers are all numbers of the form p/q, where p and q are integers and q ≠ 0.
    This is the answer i want and really appreciated for the help.
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