Find the amount at the end of 3 years and 6 months- Statement I: If a principal is invested at the rate of simple interest for 12 years it becomes 5 times. Statement II: The principal produces a compound interest of Rs. 1350 if it invested at three fourth of the same rate of interest for 2 years. Statement III: Difference between CI and SI for 3 year is Rs. 487.5

From Statement I: Principal becomes 5 times in 12 years at simple interest. Using P(1 + 12r/100) = 5P, we get r = 400/12 = 33.33% per annum. Statement II: At 3/4 of this rate (25% CI), principal earns Rs. 1350 in 2 years, giving P((1.25)^2 - 1) = 1350, so P = 2400. Statement III: Difference between CI and SI for 3 years is Rs. 487.5, which can verify the rate. With P=2400 and r=33.33%, we can calculate amount at 3.5 years using compound interest.