Find the sum to infinity of the geometric series 20 + 4 + 4/5 + ...
Answer and explanation
Correct answer: D. 25
- Step 1: The ratio is r = 1/5, and |r| < 1, so the series converges.
- Step 2: S = a/(1 - r) = 20/(1 - 1/5) = 25.
Answer
25.
Why not the others: '100' divides by r instead of 1 - r; '24' adds the first two terms only; '5' starts the sum at the second term.
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