If an amount doubles automatically in 8 years, then what is the interest rate?

A sum of money at simple interest amount to Rs.4800 in 3 years and Rs.5600 in the 5 years. The sum is

An amount doubles itself in 5 years simple interest. What is the rate of interest per year?

The difference between the compound interest and simple interest of a certain sum of amount is rupees 256.40 for 4 years at 10% rate per annum. Find the sum of money?

A sum of ₹ 10,000 is lent partly at 8 % and remaining at 10% per annum. If the yearly interest on the average is 9.2 %, the two parts are 

₹ 500 was invested at 12 % per annum simple interest and another certain sum of money invested at 10 % per annum simple interest . If the total interest on both the sum after 4 years is 480, the latter sum of money is

In a certain time, the ratio of a certain principle and interest obtained from it are in the ratio 10 : 3 at 10 % interest per annum. The number of years for which the money was invested is? 

A certain sum of money lent out at simple interest amounts to Rs. 2400 in 4 years and Rs. 3000 in 6 years. Find the rate of interest per annum?