📐 Mathematics · Sequences and Series · JEE

How many terms of AP: 18, 16, 14,... are needed for sum = 0?

Answer: 19.

Correct answer: C. 19

Explanation: Sn = 0. n/2 [2×18 + (n-1)(-2)] = 0. 36 - 2(n-1) = 0. n-1 = 18, n = 19.

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