The first term of an arithmetic progression is and its common difference is . What is the sum of its first terms?
Answer and explanation
Correct answer: B. 468
**
- Step 1: Recall the standard summation identity for an arithmetic sequence: .
- Step 2: Insert the given values , , and : .
- Step 3: Evaluating the bracketed term gives , so .
Answer
468.
Why not the others: '923' evaluates the summation using terms instead of ; '481' omits the factor of in the series formula; '463' adds rather than subtracts the common difference term.
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