ECZ 2019 · GCE Paper 1 — Sequences and Series
For the sequence −10, −7, −4, −1, …, find the sum of the first 20 terms.
- A. 370
- B. 740
- C. 570
- D. 185
Verified working — step 1
Sₙ = n2[2a + (n − 1)d] with a = −10, d = 3, n = 20: S₂₀ = 10[2(−10) + 19 × 3] = 10[−20 + 57] = 10 × 37 = …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.
Have a different question?
Search it — if it is from a past paper or a school mock, chances are we have it worked out, or one that uses the same method.
Search any past-paper question