9th Class Mathematics Number System and its Operations Question Bank Number System

  • question_answer
    The value of\[\frac{1}{\sqrt{6.25}+\sqrt{5.25}}+\frac{1}{\sqrt{4.25}+\sqrt{3.25}}+\frac{1}{\sqrt{5.25}+\sqrt{4.25}}+\frac{1}{\sqrt{3.25}+\sqrt{2.25}}\]is

    A)  1.00 

    B)  1.25

    C)  1.50                         

    D)  2.25

    Correct Answer: A

    Solution :

    (a): \[\frac{1}{\sqrt{3.25}+\sqrt{2.25}}\] =\[\frac{1}{\left( \sqrt{3.25}+\sqrt{2.25} \right)}\times \frac{\sqrt{3.25}-\sqrt{2.25}}{\sqrt{3.25}-\sqrt{2.25}}\] =\[\frac{\sqrt{3.25}-\sqrt{2.25}}{3.25-2.25}=\sqrt{3.25}-\sqrt{2.25}\] Similarly, \[\frac{1}{\sqrt{4.25}+\sqrt{3.25}}=\sqrt{4.25}-\sqrt{3.25}\] \[\frac{1}{\sqrt{5.25}+\sqrt{4.25}}=\sqrt{5.25}-\sqrt{4.25}\] \[\frac{1}{\sqrt{6.25}+\sqrt{5.25}}=\sqrt{6.25}-\sqrt{5.25}\] \[\therefore \]Expression \[=\sqrt{3.25}-\sqrt{2.25}+\sqrt{4.25}-\sqrt{3.25}+\sqrt{5.25}-\sqrt{4.25}+\sqrt{6.25}-\sqrt{5.25}\]\[=\sqrt{6.25}-\sqrt{2.25}=2.5-1.5=1\]                                    


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