Question:medium

Find the sum of the infinite geometric series: $$ S = 8 + 4 + 2 + \cdots $$ if it converges.

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Tip: The infinite geometric series sum exists only if \(|r|<1\).
Updated On: Jan 13, 2026
  • \(14\)
  • \(16\)
  • \(18\)
  • \(20\)
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The Correct Option is B

Solution and Explanation

The sum of the infinite geometric series \( S = 8 + 4 + 2 + \cdots \) is determined by first identifying the first term and the common ratio. The initial term \( a \) is 8.

The common ratio \( r \) is calculated by dividing the second term by the first term:

\( r = \frac{4}{8} = \frac{1}{2} \)

An infinite geometric series converges if the absolute value of the common ratio is less than 1, that is, \( |r| < 1 \). Here, \( |r| = \frac{1}{2} < 1 \), confirming convergence.

The formula for the sum of a convergent infinite geometric series is:

\( S = \frac{a}{1 - r} \)

Substituting the identified values:

\( S = \frac{8}{1 - \frac{1}{2}} \)

The calculation proceeds as follows:

\( S = \frac{8}{\frac{1}{2}} = 8 \times 2 = 16 \)

Therefore, the sum of the given infinite geometric series is \( 16 \).

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