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NTSE Sample Paper NTSE SAT Practice Test-19

  • question_answer
    If\[(a-b):(a+b)=1:5\], then what is \[({{a}^{2}}-{{b}^{2}}):({{a}^{2}}+{{b}^{2}})\]equal to?

    A) 2 : 3                             

    B)   3 : 2

    C) 5 : 13               

    D) 13 : 5

    Correct Answer: C

    Solution :

    [c]  \[\frac{a-b}{a+b}=\frac{1}{5}\Rightarrow \,5a-5b=a+b\,\,or\,\,2a\] \[=3\,b\,i.e.\frac{a}{b}=3/2\]             \[\therefore \frac{{{a}^{2}}-{{b}^{2}}}{{{a}^{2}}+{{b}^{2}}}=\frac{\frac{{{a}^{2}}}{{{b}^{2}}}-1}{\frac{{{a}^{2}}}{{{b}^{2}}}+1}=\frac{\frac{9}{4}-1}{\frac{9}{4}+1}=\frac{5}{13}\]    


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