Question : At a certain annual rate (rounded off to the nearest integer) of simple interest, a sum of money becomes nine times its original value in 21 years. By how much does the rate of interest change if the same sum of money has to become 12 times its original value in 25 years?

Question : A certain sum becomes 4 times of itself in 5 years at a rate of simple interest. In 15 years it will become how many times of itself at the same rate of simple interest?

Question : If a sum of money at simple interest becomes 45 times in 110 years, then in how many years will that sum become 23 times?

Question : A sum of Rs. 3000 becomes Rs. 6000 when invested in a scheme of simple interest. If the annual rate of interest and the number of years for which the sum was invested are the same, then what is the annual rate of interest?

Question : The simple interest on a sum of money in 6 years at the rate of 15% per annum is INR 1,440 less than the simple interest accrued on the same sum in 9 years at 18% per annum. What is the sum of money (in INR)?