Question

The sum of first 15 terms of an ap is 675 and next 15 terms is 2025, find the common difference

Answer 1

S[15] = (15/2)(2a+14d) S[30] = 675+2025 Now, (15/2)(2a+14d) =675 or, a+7d = 45.....(i) Similarly, (30/2)(2a+29d)=2025 And get the other equation. Perform elimination process with the two equations and get common difference(d).