ECZ 2018 · GCE Paper 1 — Sequences and Series
The first three terms of an arithmetic progression are 5, 7 and 9. Find the sum of the first 12 terms.
- A. 192
- B. 27
- C. 384
- D. 96
Verified working — step 1
Use Sₙ = n2[2a + (n − 1)d] with a = 5, d = 2, n = 12: S₁₂ = 6[10 + 11 × 2] = 6 × 32 = …The full step-by-step working and final answer are included with Premium — checked against ECZ marking standards.
Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.
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