MCQ
The sum to infinity of the progression $9 - 3 + 1 - \frac{1}{3} + .....$ is
  • A
    $9$
  • B
    $9/2$
  • $27/4$
  • D
    $15/2$

Answer

Correct option: C.
$27/4$
c
(c) 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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