Find the sum of the first 8 terms of the geometric series: 3, 6, 12, 24, ...
Answer and explanation
Correct answer: A. 765
- Step 1: Identify first term a = 3 and common ratio r = 6 / 3 = 2.
- Step 2: Use the geometric series sum formula S_n = a(r^n - 1) / (r - 1).
- Step 3: Calculate for n = 8: S_8 = 3(2^8 - 1) / (2 - 1) = 3(256 - 1) = 3 * 255 = 765.
Answer
765.
Why not the others: Option 381 computes the sum for 7 terms: 3(127) = 381. Option 1530 calculates the sum for 9 terms. Option 510 omits the leading term multiplier 3/1.
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