Question 1

A sum of ₹5,000 is invested at 10% per annum for 2 years. What is the difference between the compound interest and simple interest earned?

Accepted Answer

Step 1: Calculate Simple Interest using SI = (P × R × T) / 100 = (5000 × 10 × 2) / 100 = ₹1,000. Step 2: Calculate Compound Interest using A = P(1 + R/100)^T = 5000(1.1)^2 = 5000 × 1.21 = ₹6,050, so CI = 6050 - 5000 = ₹1,050. Step 3: Difference = CI - SI = 1050 - 1000 = ₹50.

Question 2

Rajesh borrowed ₹5,000 at a simple interest rate of 8% per annum. How much interest will he pay after 3 years?

Accepted Answer

Step 1: Use the Simple Interest formula: SI = (P × R × T) / 100. Step 2: Substitute values: SI = (5000 × 8 × 3) / 100 = 120000 / 100 = ₹1,200. Therefore, the interest is ₹1,200.

Question 3

₹5,000 becomes ₹6,050 in 2 years at compound interest. What is the rate of interest per annum?

Accepted Answer

Step 1: Use A = P(1 + r/100)^n. Step 2: 6050 = 5000(1 + r/100)^2. Step 3: (1 + r/100)^2 = 6050/5000 = 1.21. Step 4: 1 + r/100 = √1.21 = 1.1. Step 5: r/100 = 0.1, so r = 10% per annum.

Question 4

A sum becomes ₹18,000 in 2 years and ₹19,440 in 3 years at compound interest. What is the principal?

Accepted Answer

Step 1: Let principal = P and rate = r% p.a. Step 2: After 2 years: P(1 + r/100)^2 = 18000. Step 3: After 3 years: P(1 + r/100)^3 = 19440. Step 4: Divide equation 3 by equation 2: (1 + r/100) = 19440/18000 = 1.08, so r = 8%. Step 5: Substitute back: P(1.08)^2 = 18000, so P × 1.1664 = 18000, thus P = 18000/1.1664 = ₹15,432.10 ≈ ₹15,432.

Question 5

The difference between compound interest and simple interest on a sum for 2 years at 5% per annum is ₹25. What is the principal amount?

Accepted Answer

Step 1: Use the formula for 2 years: Difference = P × R² / 10000. Step 2: Substitute: 25 = P × 25 / 10000. Step 3: Solve: P = (25 × 10000) / 25 = ₹10,000.

Question 6

₹10,000 is invested at 20% per annum compound interest. What will be the amount after 1.5 years if interest is compounded half-yearly?

Accepted Answer

Step 1: When compounded half-yearly, the rate per half-year = 20/2 = 10% and time period = 1.5 × 2 = 3 half-years. Step 2: Use A = P(1 + r/100)^n where r = 10% and n = 3. Step 3: A = 10000(1 + 10/100)^3 = 10000(1.1)^3. Step 4: (1.1)^3 = 1.331, so A = 10000 × 1.331 = ₹13,310.

Question 7

A principal amount doubles itself in 5 years at compound interest. In how many years will it become 8 times at the same rate?

Accepted Answer

Step 1: If principal doubles in 5 years, then A = 2P when n = 5. Step 2: For amount to become 8 times: 8P = P(1 + r/100)^n. Step 3: Since 2P = P(1 + r/100)^5, we have (1 + r/100)^5 = 2. Step 4: For 8P: (1 + r/100)^n = 8 = 2^3 = [(1 + r/100)^5]^3 = (1 + r/100)^15. Step 5: Therefore, n = 15 years.

Question 8

Arun deposited ₹9,000 in a savings account at 7% simple interest per annum. How much total amount will he have after 2 years?

Accepted Answer

Step 1: Calculate SI using SI = (P × R × T) / 100 = (9000 × 7 × 2) / 100 = 126000 / 100 = ₹1,260. Step 2: Total Amount = Principal + SI = 9000 + 1260 = ₹10,260. Therefore, the total amount is ₹10,260.

Question 9

A principal amount earns ₹600 as simple interest in 3 years at 8% per annum. What will be the compound interest earned on the same principal at the same rate for the same period?

Accepted Answer

Step 1: Find principal using SI = (P × R × T) / 100. So 600 = (P × 8 × 3) / 100, which gives P = 2500. Step 2: Calculate CI using A = P(1 + R/100)^T = 2500(1.08)^3 = 2500 × 1.259712 = 3149.28. Step 3: CI = 3149.28 - 2500 = ₹649.28 ≈ ₹649.

Question 10

A loan of ₹15,000 is taken at 5% simple interest per annum. What is the simple interest for the first 6 months?

Accepted Answer

Step 1: Convert 6 months to years: 6 months = 6/12 = 0.5 years. Step 2: Use SI = (P × R × T) / 100 = (15000 × 5 × 0.5) / 100 = 37500 / 100 = ₹375. Therefore, the simple interest for 6 months is ₹375.

Question 11

At what rate of simple interest per annum will ₹4,500 amount to ₹5,400 in 4 years?

Accepted Answer

Step 1: Calculate SI = Amount - Principal = 5400 - 4500 = ₹900. Step 2: Use SI = (P × R × T) / 100 and rearrange for R: R = (SI × 100) / (P × T). Step 3: R = (900 × 100) / (4500 × 4) = 90000 / 18000 = 5% per annum. Therefore, the rate is 5% p.a.

Question 12

At what rate of interest per annum will the difference between compound interest and simple interest on ₹8,000 for 2 years be ₹80?

Accepted Answer

Step 1: Use the formula for difference: Difference = P × R² / 10000 (for 2 years). Step 2: Substitute: 80 = 8000 × R² / 10000. Step 3: Solve: 80 = 0.8 × R², so R² = 100, therefore R = 10% per annum.

Question 13

A sum of ₹8,000 is invested at 10% per annum compound interest. What will be the amount after 2 years?

Accepted Answer

Step 1: Use the compound interest formula A = P(1 + r/100)^n. Step 2: A = 8000(1 + 10/100)^2 = 8000(1.1)^2 = 8000 × 1.21 = ₹9,680. Therefore, the amount after 2 years is ₹9,680.

Question 14

Priya lent ₹12,000 to her friend at 6% simple interest per annum. After how many years will the interest amount to ₹2,160?

Accepted Answer

Step 1: Use SI = (P × R × T) / 100. Step 2: Rearrange for T: T = (SI × 100) / (P × R). Step 3: T = (2160 × 100) / (12000 × 6) = 216000 / 72000 = 3 years. Therefore, the time period is 3 years.

Question 15

A sum of ₹4,000 is invested at 12% per annum. If the difference between CI and SI for 2 years is ₹x, then what is the value of x?

Accepted Answer

Step 1: Calculate SI = (4000 × 12 × 2) / 100 = ₹960. Step 2: Calculate CI using A = 4000(1.12)² = 4000 × 1.2544 = 5017.6, so CI = 5017.6 - 4000 = ₹1,017.6. Step 3: Difference = 1017.6 - 960 = ₹57.6 ≈ ₹58.

Question 16

If the simple interest on ₹6,000 for 2 years is ₹1,200, what will be the compound interest on the same principal for the same period at the same rate?

Accepted Answer

Step 1: Find rate using SI = (P × R × T) / 100. So 1200 = (6000 × R × 2) / 100, which gives R = 10% per annum. Step 2: Calculate CI using A = 6000(1.10)² = 6000 × 1.21 = 7260. Step 3: CI = 7260 - 6000 = ₹1,260.

Question 17

₹12,000 is invested at 5% per annum compound interest compounded annually. What is the compound interest earned in 3 years?

Accepted Answer

Step 1: Use A = P(1 + r/100)^n. Step 2: A = 12000(1 + 5/100)^3 = 12000(1.05)^3. Step 3: (1.05)^3 = 1.157625, so A = 12000 × 1.157625 = ₹13,891.50. Step 4: Compound Interest = A - P = 13891.50 - 12000 = ₹1,891.50.

Question 18

A certain sum becomes ₹1,331 in 3 years at 10% per annum compound interest. What was the original sum?

Accepted Answer

Step 1: Use A = P(1 + r/100)^n. Step 2: 1331 = P(1 + 10/100)^3 = P(1.1)^3. Step 3: (1.1)^3 = 1.1 × 1.1 × 1.1 = 1.331. Step 4: 1331 = P × 1.331. Step 5: P = 1331/1.331 = ₹1,000.

Question 19

A sum of ₹5,000 is invested at 12% per annum compound interest, compounded half-yearly. What is the amount after 1 year?

Accepted Answer

Step 1: When compounded half-yearly, rate per half-year = 12/2 = 6% and number of periods = 1 × 2 = 2. Step 2: A = P(1 + r/100)^n = 5000(1 + 6/100)^2 = 5000(1.06)^2. Step 3: (1.06)^2 = 1.1236. Step 4: A = 5000 × 1.1236 = ₹5,618.

Question 20

The difference between compound interest and simple interest on a sum for 2 years at 8% per annum is ₹64. What is the principal?

Accepted Answer

Step 1: For 2 years, CI - SI = P × (r/100)^2. Step 2: 64 = P × (8/100)^2 = P × (0.08)^2 = P × 0.0064. Step 3: P = 64/0.0064 = ₹10,000.

IBPS RRB PO Simple & Compound Interest Questions

IBPS RRB PO Simple & Compound Interest — Past Exam Questions

Study by Subtopic — Simple & Compound Interest

Study Next — Quantitative Aptitude Topics