SSC Quantitative Aptitude Number System and its Operations Question Bank Numbers and Their Principles (II)

  • question_answer
    \[\frac{1}{1\cdot 4}+\frac{1}{4\cdot 7}+\frac{1}{7\cdot 10}+\frac{1}{10\cdot 13}+\frac{1}{13\cdot 16}\] is equal to

    A) \[\frac{1}{3}\]

    B) \[\frac{5}{16}\]

    C) \[\frac{3}{8}\]

    D) \[\frac{41}{7280}\]

    Correct Answer: B

    Solution :

    [b] Given expression \[=\frac{1}{3}\left( 1-\frac{1}{4} \right)+\frac{1}{3}\left( \frac{1}{4}-\frac{1}{7} \right)+\frac{1}{3}\left( \frac{1}{7}-\frac{1}{10} \right)+\frac{1}{3}\left( \frac{1}{10}-\frac{1}{13} \right)\] \[+\frac{1}{3}\left( \frac{1}{13}-\frac{1}{16} \right)\]             \[=\frac{1}{3}.\left\{ \begin{align}   & 1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10} \\  & +\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16} \\ \end{align} \right\}\]             \[=\frac{1}{3}\left( 1-\frac{1}{16} \right)=\left( \frac{1}{3}\times \frac{15}{16} \right)=\frac{5}{16}\]


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