Question

Find the sum of the first 20-terms of the arithmetic progression having the sum of first 10 terms as 52 and the sum of the first 15 terms as 77.

Answer 1

Let ‘a’ be the first term and d be the common difference of A.P.

Let the A.P. be a, a + d, a + 2d, ..... we are given S₁₀ = 52 and S₁₅ = 77. (i.e.)