1. If a principal amount is invested at an annual simple interest rate of 6%, in how many years will it double?

2. At an annual simple interest rate of 18%, in how many years will a principal amount become 6 times its original value?

(a) 25 years (b) 30 years (c) 31.78 years (d) 27.78 years

3. In how many years will the amounts of simple interest and compound interest be equal for the same principal at the same annual interest rate?

(a) 3 years (b) 2 years (c) 1 years (d) \(\frac{1}{2}\)

4. In how many years will a principal amount triple at an annual simple interest rate of 10%?

5. At an annual simple interest rate of 6%, in how many years will the interest on ₹\(x\) amount become ₹\(\frac{9x}{25}\)? Find the value of the time.

(a) 6 years (b) 8 years (c) 10 years (d) 12 years

6. If a principal amount doubles in 8 years at an annual compound interest rate of \(r\%\), then in how many years will it become four times?

7. If the annual simple interest rate is \(6\frac{1}{4}\%\), in how many years will any principal amount double with interest?

(a) 5 years (b) 10 years (c) 16 years (d) 12 years

8. At an annual simple interest rate of \(6\frac{1}{4}\%\), in how many years will a sum of money double?

9. Sure! The Bengali sentence: **"কোনো মূলধন বার্ষিক 6 \(\frac{1}{4}\)% সরল সুদের হারে কত বছরে দ্বিগুণ হবে তা লিখি ।"** translates to English as: **"Write how many years it will take for a principal to double at an annual simple interest rate of 6 \(\frac{1}{4}\)%."** Would you like help solving this too?

10. At an annual compound interest rate of 4%, in how many years will a principal amount of ₹40,000 accumulate to ₹46,656?

11. At a simple interest rate of 20%, in how many years will a principal amount triple?

(a) 10 years (b) 15 years (c) 20 years (d) 5 years

12. Write down the calculation to determine in how many years a simple interest of ₹168 will be earned on a principal of ₹600 at an annual rate of 8%.

13. Write how many years it will take for a principal to double at an annual simple interest rate of 6 \(\frac{1}{4}\)%.

14. At an annual simple interest rate of 5%, a person deposits some money in the bank. After 5 years, how much total amount will he receive, if the principal is 12,500 rupees less than the total amount (principal + interest?

15. If a certain amount of money triples in 20 years, then at the same simple interest rate, in how many years will it double?

16. At an annual interest rate of 5%, for how many years will the interest on 300 rupees amount to 120 rupees?

(a) 4 (b) 8 (c) 12 (d) 12\(\frac{1}{2}\)

17. If the total amount becomes 966 rupees at an annual simple interest rate of 3% in 5 years, the principal amount will be -

(a) 480 rupees (b) 408 rupees (c) 404 rupees (d) 840 rupees

18. At an annual simple interest rate of 5%, how many years will it take for the interest on ₹6000 to become ₹1500?

(a) 3 years (b) 30 years (c) 5 years (d) 15 years

19. In how many years will the ratio of the principal and the interest earned become 10:3 at a simple interest rate of 10% per annum?

(a) 12 years (b) 3 years (c) 10 years (d) 13 years

20. At an annual simple interest rate of 8%, in how many years will 5000 rupees grow to 7400 rupees?

(a) 3 years (b) 4 years (c) 5 years (d) 6 years

21. At an annual simple interest rate of \(6\cfrac{1}{4}\%\), how much principal amount will yield a daily interest of 1 rupee?

(a) ₹ 5840 (b) ₹ 6400 (c) ₹ 5000 (d) ₹ 6000

22. At an annual simple interest rate of 8%, how much interest will make the principal amount grow to \(\cfrac{7}{5}\) times its original value?

(a) 4 years (b) 5 years (c) 6 years (d) 7 years

23. If a certain principal amount triples in 15 years at simple interest, then the annual rate of simple interest will be —

(a) \(13\frac{1}{3}\%\) (b) \(12\frac{1}{3}\%\) (c) \(11\frac{1}{3}\%\) (d) \(10\frac{1}{3}\%\)

24. If a sum of money becomes 4 times its original amount in *n* years at a fixed annual compound interest rate, then in how many years will it become 4 times?

25. If a certain amount of money doubles in 4 years at a fixed annual compound interest rate, in how many years will it become four times?

26. At an annual interest rate of 4%, what principal amount will yield at least ₹80 difference between simple interest and compound interest over 2 years?

27. If the simple interest for \(n\) years at an annual rate of \(r\%\) is \(\frac{pnr}{25}\) rupees, then the principal amount will be _____ rupees.

28. A farmer deposited some money in the village post office. After 4 years, he found that the total amount including interest had become ₹434. He calculated that the interest he received was \(\frac{6}{25}\) of his principal amount. Find how much money he had originally deposited and what annual rate of simple interest the post office gave.

29. A borrowed ₹960 from B at an annual simple interest rate of 6%, with the condition that the loan will be repaid over the next 4 yearly installments. In the first 3 installments, A will pay only one-fourth of the principal each year. In the final (4th) installment, A will pay the remaining principal along with the total interest accrued over the 4 years. Find the total amount A will pay at the end of the 4th year.

30. If the total simple interest on a principal amount at an annual rate of \(x\%\) for \(y\) years is \(\frac{pyx}{25}\) rupees, then the principal amount will be:

(a) \(2p\) rupees (b) \(4p\) rupees (c) \(\cfrac{p}{2}\) rupees (d) \(\cfrac{p}{4}\) rupees