Engineering Board Exam Reviewer · Sequences and Series · medium
The 8th term of an arithmetic progression is 12 and the 39th term is 43. What is the sum of the first 30 terms?
- 585
- 475
- 805
- 625
Answer
A. 585
Solution
d = 43-12/39-8 = 1, so a1 = 12-7(1) = 5. Sum of the first 30 terms = 30/2(2(5)+29(1)) = 15(39) = 585.
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