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NTSE Sample Paper NTSE SAT Practice Test-8

  • question_answer
    if\[a=\frac{xy}{x+y},b=\frac{xz}{x+z}\]and  \[c=\frac{yz}{y+z}\] where a, b, c are non-zero, then what is value of x?

    A) \[\frac{2abc}{ac+bc-ab}\] 

    B)                     \[\frac{2abc}{ab-ac+bc}\]

    C) \[\frac{2abc}{ab+bc+ca}\]              

    D) \[\frac{2abc}{ab+ac-bc}\]

    Correct Answer: A

    Solution :

    [a] \[\frac{1}{a}=\frac{1}{x}+\frac{1}{y};\frac{1}{b}=\frac{1}{x}+\frac{1}{z};\frac{1}{c}=\frac{1}{y}+\frac{1}{z}\] \[\Rightarrow \,\,\,\,\frac{1}{b}+\frac{1}{a}-\frac{1}{c}=\frac{2}{x}\] \[\Rightarrow \,\,\,\,x=\frac{2abc}{bc+ac-ab}\]


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