The simple interest accrued on a sum of money in 8 years is 1024. If the principal is quadrupled after 5 years then what will be the total interest at the end of 8 years?

Let P be the principal and R be the annual interest rate. Interest for 8 years at simple interest: I₁ = P×R×8 = 1024, so P×R = 128. When principal is quadrupled after 5 years: for first 5 years, interest Iₐ = P×R×5 = 128×5 = 640. For remaining 3 years on 4P: Iᵦ = 4P×R×3 = 12×P×R = 12×128 = 1536. Total interest = 640 + 1536 = 2176. Therefore, the total interest at the end of 8 years is Rs. 2176.