Question

Let A₁ , A₂ , A₃ be the three A.P. with the same common difference d and having their first terms as A, A + 1, A + 2, respectively. Let a, b, c be the 7^th, 9^th, 17^th terms of A₁ , A₂ , A₃ , respectively such that \(\begin{vmatrix} a & 7 & 1 \\ 2b & 17 & 1 \\ c & 17 & 1 \end{vmatrix}+70=0\)

If a = 29, then the sum of first 20 terms of an AP whose first term is c – a – b and common difference is d/12 , is equal to ______ .

Answer 1

Correct answer is 495