JEE Main & Advanced Mathematics Sequence & Series Question Bank Geometric Progression

  • question_answer
    The sum to infinity of the progression \[9-3+1-\frac{1}{3}+.....\] is  [Karnataka CET 2005]

    A) 9

    B) 9/2

    C) 27/4

    D) 15/2

    Correct Answer: C

    Solution :

    Infinite series \[9-3+1-\frac{1}{3}......\infty \] is a G.P. with \[a=9,r=\frac{-1}{3}\] \ \[{{S}_{\infty }}=\frac{a}{1-r}=\frac{9}{1+\left( \frac{1}{3} \right)}=\frac{9\times 3}{4}=\frac{27}{4}\].


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