ECZ 2025 · GCE Paper 1 — Sequences and Series
The formula for the nth term of an arithmetic progression is 2n − 3. Find the common difference, d, if the sum of the first 8 terms is 48.
- A. −2
- B. 4
- C. 2
- D. 7
Verified working — step 1
With a = −1, use S₈ = (82)[2a + 7d]: 48 = 4[−2 + 7d], so 12 = −2 + 7d, 7d = 14, d = …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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