Compound Interest Quiz - ICSE Class 9 Mathematics

Free practice quiz: Compound Interest (ICSE Class 9 Mathematics). 19 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This ICSE Class 9 Mathematics practice quiz has 19 multiple-choice questions on Compound Interest, and 19 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. Find the principal which yields ₹205 compound interest in 2 years at 5% per annum.

   1. ₹1000
   2. ₹2000
   3. ₹3000
   4. ₹4000
   Show answer

   Answer: B. ₹2000

   Let the principal be P. Rate (r) = 5%, Time (n) = 2 years. Compound Interest (CI) = P[(1 + r/100)^n - 1] 205 = P[(1 + 5/100)^2 - 1] 205 = P[(1.05)^2 - 1] 205 = P[1.1025 - 1] 205 = P[0.1025] P = 205 / 0.1025 P = 2000 So, the principal is ₹2000.

2. If the compound interest on a sum for 2 years at 10% per annum is ₹210, find the principal.

   1. ₹1000
   2. ₹1500
   3. ₹2000
   4. ₹2100
   Show answer

   Answer: A. ₹1000

   Let the principal be P. Rate (r) = 10%, Time (n) = 2 years. Compound Interest (CI) = P[(1 + r/100)^n - 1] 210 = P[(1 + 10/100)^2 - 1] 210 = P[(1.1)^2 - 1] 210 = P[1.21 - 1] 210 = P[0.21] P = 210 / 0.21 P = 1000 So, the principal is ₹1000.

3. A sum of money doubles itself in 5 years at compound interest. In how many years will it become 4 times itself?

   1. 10 years
   2. 15 years
   3. 20 years
   4. 25 years
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   Answer: A. 10 years

   Let the principal be P. If the sum doubles in 5 years, then A = 2P after 5 years. 2P = P(1 + r/100)^5 2 = (1 + r/100)^5 We want to find the time (n) when the sum becomes 4 times itself (4P). 4P = P(1 + r/100)^n 4 = (1 + r/100)^n Since 4 = 2^2, we can substitute 2 = (1 + r/100)^5: [(1 + r/100)^5]^2 = (1 + r/100)^n (1 + r/100)^{5 imes 2} = (1 + r/100)^n (1 + r/100)^{10} = (1 + r/100)^n Therefore, n = 10 years. If a sum becomes k times itself in t years, it becomes k^m times itself in m*t years.

4. A sum of money triples itself in 8 years at compound interest. How many years will it take for the sum to become 9 times itself?

   1. 16 years
   2. 20 years
   3. 24 years
   4. 32 years
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   Answer: A. 16 years

   Let the principal be P. If the sum triples in 8 years, then A = 3P after 8 years. 3P = P(1 + r/100)^8 3 = (1 + r/100)^8 We want to find the time (n) when the sum becomes 9 times itself (9P). 9P = P(1 + r/100)^n 9 = (1 + r/100)^n Since 9 = 3^2, we can substitute 3 = (1 + r/100)^8: [(1 + r/100)^8]^2 = (1 + r/100)^n (1 + r/100)^{8 imes 2} = (1 + r/100)^n (1 + r/100)^{16} = (1 + r/100)^n Therefore, n = 16 years. If a sum becomes k times itself in t years, it becomes k^m times itself in m*t years.

5. Find the principal that amounts to ₹13310 in 3 years at 10% per annum compound interest.

   1. ₹10000
   2. ₹11000
   3. ₹12000
   4. ₹13000
   Show answer

   Answer: A. ₹10000

   Amount (A) = ₹13310 Rate (r) = 10% per annum Time (n) = 3 years Amount (A) = P(1 + r/100)^n 13310 = P(1 + 10/100)^3 13310 = P(1.1)^3 13310 = P * 1.331 P = 13310 / 1.331 P = 10000 So, the principal is ₹10000.

More questions in this quiz

Answers and explanations are in the full quiz.

1. A sum of money amounts to ₹9261 in 3 years at 5% per annum compound interest. What is the principal?
2. At what rate percent per annum will ₹4000 amount to ₹4630.50 in 3 years at compound interest?
3. A sum of money at compound interest amounts to ₹5290 in 2 years and ₹5819 in 3 years. Find the rate of interest.
4. What is the principal if the compound interest for 3 years is ₹129.60 and the rate of interest is 8% per annum?
5. A sum of money invested at compound interest amounts to ₹14641 in 4 years. If the rate of interest is 10% per annum, what is the principal?
6. Find the amount when ₹15000 is invested at 10% per annum compound interest for 2 years, compounded annually.
7. A sum of ₹20000 amounts to ₹23152.50 in 3 years at compound interest. Find the rate of interest.
8. What is the difference between the compound interest and simple interest on ₹10000 for 2 years at 5% per annum?
9. Find the amount when ₹25000 is invested at 4% per annum compound interest for 3 years, compounded annually.
10. On what sum will the compound interest for 3 years at 10% per annum be ₹3310?
11. A sum of money becomes ₹66550 in 3 years at 10% per annum compound interest. What is the principal?
12. What is the compound interest on ₹12000 at 5% per annum for 2 years?
13. What is the principal if the amount after 2 years at 8% per annum compound interest is ₹29160?
14. A sum of money becomes ₹13230 in 2 years at 5% per annum compound interest. What is the principal?

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