A sum of Rs. 20000 was invested in a scheme. The rate of

Solution

The total interest rate for the first 3 years is 10 + 6 + 4 = 20% and after that the interest is compounded annually for 3 years at the rate of 20% per annum. The total amount received from the first investment = 120% of 20000 = 24000 Now, 18000 is invested for 3 years at 20% compound interest per year. By the net % effect formula, we can calculate the total % increase in amount. So, at the rate of 20% for 3 years, we get 72.8% as the total percentage increase. Hence, the final amount received will be 172.8% × 24000 172.8% of total investment = 172.8% × 24000 = 41472 So, the total interest earned in 6 years period = 41472 – 24000 = Rs. 21472.