SSC Sample Paper SSC CGL - Sample Paper-18

  • question_answer
    \[\frac{1}{\sqrt{9}-\sqrt{8}}-\frac{1}{\sqrt{8}-\sqrt{7}}+\frac{1}{\sqrt{7}-\sqrt{6}}-\frac{1}{\sqrt{6}-\sqrt{5}}+\frac{1}{\sqrt{5}-\sqrt{4}}\] is equal to

    A) 5                     

    B) 1         

    C) 3                                 

    D) 0

    Correct Answer: A

    Solution :

    \[\frac{1}{\sqrt{9}-\sqrt{8}}=\frac{1}{\sqrt{9}-\sqrt{8}}\times \frac{\sqrt{9}+\sqrt{8}}{\sqrt{9}+\sqrt{8}}=\frac{\sqrt{9}+\sqrt{8}}{9-8}\] Expression \[=(\sqrt{9}+\sqrt{8})-(\sqrt{8}+\sqrt{7})+(\sqrt{7}+\sqrt{6})-(\sqrt{6}\sqrt{5})\] \[+(\sqrt{5}+\sqrt{4})\] \[=\sqrt{9}+\sqrt{8}-\sqrt{8}-\sqrt{7}+\sqrt{7}+\sqrt{6}-\sqrt{6}-\sqrt{5}\] \[+\sqrt{5}+\sqrt{4}\] \[=\sqrt{9}+\sqrt{4}=3+2=5\]  


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