Answer: n(a+l)/2.
- A n(a+l)/2
- B na + ld
- C n(a-l)/2
- D (a+l)/2
Correct answer: A. n(a+l)/2
Explanation: Sn = n(a+l)/2 = n/2 × (first term + last term).
Bar heights for AP 2, 5, 8, 11 with the common difference d=3 marked between consecutive terms.
Concept context
Arithmetic progressions, geometric progressions, and sums