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Math Help - surd help urgent

  1. #1
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    Exclamation surd help urgent

    the question states "write an irrational fraction that when rationalised the solution is 5. prove"

    please help me its really urgent

    your help would be much appreciated
    Last edited by mini; March 16th 2007 at 06:50 PM.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by mini View Post
    the question states "write an irrational fraction that when rationalised the solution is 5. prove"

    please help me its really urgent

    your help would be much appreciated
    Are you sure that the question says "irrational fraction"? such usage is
    quite unusual.

    However lets try:

    sqrt(125)/sqrt(5) = sqrt(5*25)/sqrt(5) = [sqrt(25) sqrt(5)] / sqrt(5) = sqrt(25) = 5.

    RonL
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  3. #3
    Grand Panjandrum
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    Don't make multiple posts of the same question, it confuses the system and wastes the helper time.

    RonL
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  4. #4
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    Wink

    hi i think thats correct if it can be a surd over a surd can u explain how u got it

    thanks
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  5. #5
    Grand Panjandrum
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    Quote Originally Posted by mini View Post
    hi i think thats correct if it can be a surd over a surd can u explain how u got it

    thanks
    Well I needed two surds one of which was 5 times the other, so anything
    like 5 sqrt(n) and sqrt(n) will do, Now 5 sqrt(n) = sqrt(25 n), so now we
    choose any n and sqrt(25 n)/sqrt(n) will do the trick, as long as n is not a
    perfect square when the numerator and denominator will be integers -
    which we do not want.

    RonL
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  6. #6
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    thanks for your help but square root125/ square root 5 is a rational number it has to be irrational
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  7. #7
    Grand Panjandrum
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    Quote Originally Posted by mini View Post
    thanks for your help but square root125/ square root 5 is a rational number it has to be irrational
    No it has to be rational when all reduced to lowest form, as it has to
    be 5, which is an integer but may be written 5/1 so is rational.

    What you want is for both the numerator and denominator to be irrational,
    as sqrt(125) and sqrt(5) are.

    (there is no irrational number equal to 5)

    RonL
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  8. #8
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    ok thanks for your help you might be able to help with my other question the heading is money and investment thnkyou heaps and heaps
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