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Simple Interest — Questions and Answers

Simple Interest is calculated only on the original principal, so the interest earned each year is identical. That constancy is what makes SI questions quick: the interest for any number of years is just a multiple of the one-year interest. Bank clerical, SSC and railway exams almost always include one direct SI question and one comparison question with compound interest.

26 solved questionsArithmetic AptitudeFree · no signup

Simple Interest— Concepts, Formulas & Shortcuts

  • SI = P × R × T / 100, where P = principal, R = rate % per annum, T = time in years.
  • Amount A = P + SI = P(1 + RT/100).
  • Interest is the same every year, so SI for n years = n × (SI for 1 year).
  • If a sum becomes n times itself in T years, then R = 100(n − 1)/T.
  • Convert months to years before substituting: 6 months = 0.5 year, 73 days = 73/365 year.
  • Given the amount after two different periods, the difference divided by the year gap gives the yearly interest.

Simple Interest Practice Questions with Answers

Attempt each question first, then open the explanation. All 26 questions below are free to read and require no signup.

  1. Q1.The simple interest on ₹6,250 at 4% per annum for 6 months is:

    Easy
    • A₹100
    • B₹125
    • C₹150
    • D₹250
    +Show Answer & Explanation

    Answer: B. ₹125

    Explanation: SI = 6250 × 4 × 0.5/100 = ₹125.

    Simple Interest question 1 of 26

  2. Q2.A sum amounts to ₹720 in 2 years and ₹1,020 in 5 years at simple interest. The sum is:

    Moderate
    • A₹500
    • B₹520
    • C₹550
    • D₹600
    +Show Answer & Explanation

    Answer: B. ₹520

    Explanation: Interest for 3 years = 1020 − 720 = ₹300 → ₹100 per year. Principal = 720 − 2 × 100 = ₹520.

    Simple Interest question 2 of 26

  3. Q3.At what rate per annum will ₹5,000 yield ₹1,500 as simple interest in 5 years?

    Easy
    • A5%
    • B6%
    • C7%
    • D8%
    +Show Answer & Explanation

    Answer: B. 6%

    Explanation: 1500 = 5000 × R × 5/100 = 250R → R = 6%.

    Simple Interest question 3 of 26

  4. Q4.In what time will ₹4,000 amount to ₹5,000 at 5% per annum simple interest?

    Easy
    • A4 years
    • B5 years
    • C6 years
    • D8 years
    +Show Answer & Explanation

    Answer: B. 5 years

    Explanation: SI = 1000 = 4000 × 5 × T/100 = 200T → T = 5 years.

    Simple Interest question 4 of 26

  5. Q5.A sum of money doubles itself in 8 years at simple interest. The rate per annum is:

    Moderate
    • A10%
    • B12%
    • C12.5%
    • D15%
    +Show Answer & Explanation

    Answer: C. 12.5%

    Explanation: Interest = principal, so R × 8 = 100 → R = 12.5%.

    Simple Interest question 5 of 26

  6. Q6.The simple interest on ₹800 for 3 years at 6.5% per annum is:

    Easy
    • A₹144
    • B₹150
    • C₹156
    • D₹160
    +Show Answer & Explanation

    Answer: C. ₹156

    Explanation: SI = 800 × 6.5 × 3/100 = ₹156.

    Simple Interest question 6 of 26

  7. Q7.A sum becomes three times itself in 12 years at simple interest. In how many years will it become four times?

    Difficult
    • A15 years
    • B16 years
    • C18 years
    • D20 years
    +Show Answer & Explanation

    Answer: C. 18 years

    Explanation: Tripling means interest = 2P in 12 years, so interest = P in 6 years. Quadrupling needs interest = 3P → 18 years.

    Simple Interest question 7 of 26

  8. Q8.The difference between the simple interest on ₹5,000 for 3 years at 8% and at 5% per annum is:

    Easy
    • A₹400
    • B₹450
    • C₹500
    • D₹550
    +Show Answer & Explanation

    Answer: B. ₹450

    Explanation: Difference = 5000 × 3 × (8 − 5)/100 = 5000 × 9/100 = ₹450.

    Simple Interest question 8 of 26

  9. Q9.The simple interest on ₹2,000 at 5% per annum for 3 years is:

    Easy
    • A₹200
    • B₹250
    • C₹300
    • D₹350
    +Show Answer & Explanation

    Answer: C. ₹300

    Explanation: SI = 2000 × 5 × 3/100 = ₹300.

    Simple Interest question 9 of 26

  10. Q10.At what rate will ₹1,200 amount to ₹1,560 in 3 years at simple interest?

    Moderate
    • A8%
    • B10%
    • C12%
    • D15%
    +Show Answer & Explanation

    Answer: B. 10%

    Explanation: SI = 360 = 1200 × R × 3/100 = 36R → R = 10%.

    Simple Interest question 10 of 26

  11. Q11.A sum triples itself in 20 years at simple interest. The rate per annum is:

    Moderate
    • A8%
    • B10%
    • C12%
    • D15%
    +Show Answer & Explanation

    Answer: B. 10%

    Explanation: Interest = 2P over 20 years → 2 = R × 20/100 → R = 10%.

    Simple Interest question 11 of 26

  12. Q12.The simple interest on ₹4,500 at 8% per annum for 9 months is:

    Moderate
    • A₹240
    • B₹270
    • C₹300
    • D₹360
    +Show Answer & Explanation

    Answer: B. ₹270

    Explanation: 9 months = 0.75 year → SI = 4500 × 8 × 0.75/100 = ₹270.

    Simple Interest question 12 of 26

  13. Q13.In how many years will ₹6,000 yield ₹1,800 as simple interest at 6% per annum?

    Easy
    • A4 years
    • B5 years
    • C6 years
    • D7 years
    +Show Answer & Explanation

    Answer: B. 5 years

    Explanation: 1800 = 6000 × 6 × T/100 = 360T → T = 5 years.

    Simple Interest question 13 of 26

  14. Q14.A sum of ₹8,000 becomes ₹10,400 in 4 years at simple interest. The rate is:

    Moderate
    • A6%
    • B7.5%
    • C8%
    • D10%
    +Show Answer & Explanation

    Answer: B. 7.5%

    Explanation: SI = 2400 = 8000 × R × 4/100 = 320R → R = 7.5%.

    Simple Interest question 14 of 26

  15. Q15.The simple interest on a sum for 5 years at 8% per annum is ₹2,000. The sum is:

    Easy
    • A₹4,000
    • B₹5,000
    • C₹6,000
    • D₹8,000
    +Show Answer & Explanation

    Answer: B. ₹5,000

    Explanation: P = SI × 100/(R × T) = 2000 × 100/40 = ₹5,000.

    Simple Interest question 15 of 26

  16. Q16.A sum of ₹1,000 is lent partly at 5% and partly at 8% simple interest. If the total annual interest is ₹65, the amount lent at 8% is:

    Difficult
    • A₹400
    • B₹500
    • C₹600
    • D₹700
    +Show Answer & Explanation

    Answer: B. ₹500

    Explanation: Let x be lent at 8%: 0.08x + 0.05(1000 − x) = 65 → 0.03x = 15 → x = ₹500.

    Simple Interest question 16 of 26

  17. Q17.The simple interest on ₹3,000 for 2 years is ₹480. The rate per annum is:

    Easy
    • A6%
    • B7%
    • C8%
    • D9%
    +Show Answer & Explanation

    Answer: C. 8%

    Explanation: 480 = 3000 × R × 2/100 = 60R → R = 8%.

    Simple Interest question 17 of 26

  18. Q18.A sum doubles in 10 years at simple interest. In how many years will it become five times?

    Difficult
    • A30 years
    • B35 years
    • C40 years
    • D50 years
    +Show Answer & Explanation

    Answer: C. 40 years

    Explanation: Doubling means interest = P in 10 years. Five times needs interest = 4P → 40 years.

    Simple Interest question 18 of 26

  19. Q19.The simple interest on ₹1,500 at 6% per annum for 4 years is:

    Easy
    • A₹300
    • B₹330
    • C₹360
    • D₹400
    +Show Answer & Explanation

    Answer: C. ₹360

    Explanation: SI = 1500 × 6 × 4/100 = ₹360.

    Simple Interest question 19 of 26

  20. Q20.A sum of ₹2,500 gives ₹500 as simple interest in 4 years. The rate is:

    Moderate
    • A4%
    • B5%
    • C6%
    • D8%
    +Show Answer & Explanation

    Answer: B. 5%

    Explanation: 500 = 2500 × R × 4/100 = 100R → R = 5%.

    Simple Interest question 20 of 26

  21. Q21.In how many years will ₹3,000 earn ₹720 at 6% per annum simple interest?

    Moderate
    • A3 years
    • B4 years
    • C5 years
    • D6 years
    +Show Answer & Explanation

    Answer: B. 4 years

    Explanation: 720 = 3000 × 6 × T/100 = 180T → T = 4 years.

    Simple Interest question 21 of 26

  22. Q22.The amount on ₹1,200 at 10% simple interest for 3 years is:

    Easy
    • A₹1,440
    • B₹1,500
    • C₹1,560
    • D₹1,600
    +Show Answer & Explanation

    Answer: C. ₹1,560

    Explanation: SI = ₹360, so amount = 1200 + 360 = ₹1,560.

    Simple Interest question 22 of 26

  23. Q23.At what rate will a sum double itself in 20 years at simple interest?

    Moderate
    • A4%
    • B5%
    • C6%
    • D8%
    +Show Answer & Explanation

    Answer: B. 5%

    Explanation: Interest = principal → R × 20 = 100 → R = 5%.

    Simple Interest question 23 of 26

  24. Q24.The simple interest on ₹900 for 2 years at 4% per annum is:

    Easy
    • A₹64
    • B₹72
    • C₹80
    • D₹90
    +Show Answer & Explanation

    Answer: B. ₹72

    Explanation: SI = 900 × 4 × 2/100 = ₹72.

    Simple Interest question 24 of 26

  25. Q25.A sum of money becomes ₹2,400 in 3 years and ₹2,600 in 4 years at simple interest. The principal is:

    Difficult
    • A₹1,600
    • B₹1,800
    • C₹2,000
    • D₹2,200
    +Show Answer & Explanation

    Answer: B. ₹1,800

    Explanation: Annual interest = 2600 − 2400 = ₹200. Principal = 2400 − 3 × 200 = ₹1,800.

    Simple Interest question 25 of 26

  26. Q26.The simple interest on ₹10,000 at 7% per annum for 6 months is:

    Easy
    • A₹300
    • B₹350
    • C₹400
    • D₹700
    +Show Answer & Explanation

    Answer: B. ₹350

    Explanation: 6 months = 0.5 year → SI = 10000 × 7 × 0.5/100 = ₹350.

    Simple Interest question 26 of 26

Simple Interest — Frequently Asked Questions

How do I find the principal when only two amounts are given?+

Subtract the two amounts to get the interest for the intervening years, divide by the number of years to get the annual interest, then subtract the accumulated interest from either amount.

In how many years does a sum double at simple interest?+

The interest must equal the principal, so P = P·R·T/100 ⇒ R·T = 100. At 10% it doubles in 10 years; at 12.5% in 8 years.

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