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Sum the first 15 terms of the AP 3, 7, 11, …
A345
B465
C525
D540
Answer & Solution
Correct answer: B. 465
a = 3, d = 4, n = 15. Sₙ = 15/2 [6 + 14·4] = 15/2 × 62 = 15 × 31 = 465.
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