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Question

The difference between a positive proper fraction and its reciprocal is \(\frac{9}{20}\)  .The fraction is:

Options:
A .  \(\frac{3}{5}\)
B .  \(\frac{3}{10}\)
C .  \(\frac{4}{5}\)
D .  \(\frac{4}{3}\)
Answer: Option C

Let the required fraction be x. Then \(\frac{1}{x}-x = \frac{9}{20}\)


Therefore \(\frac{1-x^{2}}{x} = \frac{9}{20}\)


   20 - 20x2 = 9x


      20x2 + 9x - 20 = 0


      20x2 + 25x - 16x - 20 = 0


      5x(4x + 5) - 4(4x + 5) = 0


(4x + 5)(5x - 4) = 0


\(x = \frac{4}{5}\)


 


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Very hard



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