Find the sum to infinity of the geometric series 9 + 3 + 1 + ...
Answer and explanation
Correct answer: B. 13.5
- Step 1: The ratio is r = 1/3, and |r| < 1, so the series converges.
- Step 2: S = a/(1 - r) = 9/(1 - 1/3) = 13.5.
Answer
13.5.
Why not the others: '27' divides by r instead of 1 - r; '12' adds the first two terms only; '4.5' starts the sum at the second term.
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