We have covered the Simple Interest & Compound Interest chapter thoroughly, starting with the concepts and formulas and then moving to questions on Simple Interest, Compound Interest, Difference Between Simple Interest & Compound Interest, Compound Growth, and Depreciation.
We have also completed a dedicated Simple Interest & Compound Interest Practice Questions section.
Now it is time to move to Previous Year Questions (PYQs) and see how Simple Interest and Compound Interest concepts are actually tested in competitive examinations.
The questions on this page are taken from SSC, RRB, Banking, Defence, and other competitive examinations and are provided with complete solutions.
Before jumping to the solution, read each question carefully, identify the concept being tested, and try to solve it using your own understanding. The purpose of PYQs is not only to get the answer but also to understand how examiners frame questions and how familiar concepts are applied in real examinations.
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You can also continue with the Simple Interest & Compound Interest learning cluster through the related resources linked throughout this page.
Now, let’s begin with the Simple Interest & Compound Interest PYQs and move one step further from learning the concepts to experiencing how they appear in real competitive examinations.
Question 1: A candidate preparing for an RRB examination invests ₹7,800 at 5% compound interest per annum, compounded annually. How much compound interest will be earned after 3 years? (RRB NTPC)
Solution
Given:
Principal = ₹7,800
Rate = 5% per annum
Time = 3 years
Amount = Principal × (1 + Rate/100)^n
= ₹7,800 × (1 + 5/100)^3
= ₹7,800 × (1.05)^3
= ₹7,800 × 1.157625
= ₹9,029.475
Compound Interest = Amount − Principal
= ₹9,029.475 − ₹7,800
= ₹1,229.475
Answer: ₹1,229.48 (approximately)
Question 2: A candidate preparing for SSC CGL invests ₹10,000 at 4% compound interest per annum, compounded half-yearly. What will be the compound interest earned after 2 years? (SSC CGL)
Solution
Principal = ₹10,000
Rate = 4% per annum
Time = 2 years
Compounding = Half-yearly
Rate per half-year = 4% ÷ 2 = 2%
Number of half-years = 2 × 2 = 4
Amount = Principal × (1 + Rate/100)^n
= ₹10,000 × (1 + 2/100)^4
= ₹10,000 × (1.02)^4
= ₹10,000 × 1.08243216
= ₹10,824.3216
Compound Interest = Amount − Principal
= ₹10,824.3216 − ₹10,000
= ₹824.3216
Answer: ₹824.32 (approximately)
Question 3: A candidate preparing for SSC CHSL invests ₹1,600 in a scheme offering compound interest annually. The investment grows to ₹1,852.20 after 3 years. What is the annual rate of compound interest? (IBPS)
Solution
Principal = ₹1,600
Amount = ₹1,852.20
Time = 3 years
Amount = Principal × (1 + Rate/100)^n
₹1,852.20 = ₹1,600 × (1 + Rate/100)^3
₹1,852.20 ÷ ₹1,600 = (1 + Rate/100)^3
1.157625 = (1 + Rate/100)^3
Since:
1.157625 = 1.05 × 1.05 × 1.05
Therefore:
1 + Rate/100 = 1.05
Rate/100 = 0.05
Rate = 5%
Answer: 5% per annum
Shortcut For SSC, RRB, Defence, Banking, Police
Amount / Principal = (1 + R/100)^T
Here:
₹1,852.20 / ₹1,600 = 1.157625 = (21/20)^3
So,
1 + R/100 = 21/20
Therefore:
R = 5% per annum
Answer: 5% per annum
Question 4: Apsara invests a certain sum at 5% compound interest per annum. After 3 years, the difference between the compound interest and simple interest earned on the sum is ₹15.25. Find the sum invested. (SSC CGL)
Solution
Principal = P
Rate = 5% per annum
Time = 3 years
Difference between CI and SI = ₹15.25
For 3 years:
Difference (CI − SI) = P × R² × (300 + R) ÷ 100³
15.25 = P × 5² × (300 + 5) ÷ 100³
15.25 = P × 25 × 305 ÷ 10,00,000
15.25 = P × 7,625 ÷ 10,00,000
P = 15.25 × 10,00,000 ÷ 7,625
P = ₹2,000
Answer: ₹2,000
Question 5: A Section Controller purchases a laptop for home and work use at a cash price of ₹19,650. He pays ₹3,100 as the cash down payment and agrees to pay the remaining amount in three equal annual installments. If the financing cost is charged at 10% compound interest per annum, compounded annually, what is the amount of each instalment? (SSC CGL)
Solution
Cash price = ₹19,650
Down payment = ₹3,100
Remaining amount = ₹19,650 − ₹3,100
= ₹16,550
Let each annual instalment = ₹X.
Using:
A = P × (1 + R/100)^N
For the 1st instalment:
P = X ÷ 1.10
For the 2nd instalment:
P = X ÷ (1.10)^2
For the 3rd instalment:
P = X ÷ (1.10)^3
The three instalments together make up the remaining amount:
X/1.10 + X/(1.10)^2 + X/(1.10)^3 = ₹16,550
Substituting:
X/1.10 + X/1.21 + X/1.331 = ₹16,550
X × (10/11 + 100/121 + 1000/1331) = ₹16,550
X × 3310/1331 = ₹16,550
X = ₹16,550 × 1331/3310
X = ₹6,655
Answer: ₹6,655 per instalment
Question 6: A candidate preparing for the RRB NTPC examination invests ₹10,000 at compound interest. The rate is 4% per annum in the first year, 5% per annum in the second year, and 6% per annum in the third year. What will be the compound interest earned after 3 years? (SSC CPO)
Solution
Principal = ₹10,000
Rate in 1st year = 4%
Rate in 2nd year = 5%
Rate in 3rd year = 6%
Using the successive compound growth method:
Amount after 1st year:
₹10,000 × (1 + 4/100)
= ₹10,000 × 1.04
= ₹10,400
Amount after 2nd year:
₹10,400 × (1 + 5/100)
= ₹10,400 × 1.05
= ₹10,920
Amount after 3rd year:
₹10,920 × (1 + 6/100)
= ₹10,920 × 1.06
= ₹11,575.20
Compound Interest = Amount − Principal
= ₹11,575.20 − ₹10,000
= ₹1,575.20
Answer: ₹1,575.20
Shortcut
Instead of calculating year by year:
Amount = ₹10,000 × (1 + 4/100) × (1 + 5/100) × (1 + 6/100)
= ₹10,000 × 1.04 × 1.05 × 1.06
= ₹11,575.20
Therefore:
Compound Interest = ₹11,575.20 − ₹10,000
= ₹1,575.20
Question 7: A candidate preparing for a Paramedical examination deposits ₹800 at 10% compound interest per annum, compounded half-yearly. In how much time will the deposit grow to ₹926.10? (SSC GD)
Solution
Principal = ₹800
Rate = 10% per annum
Compounding = Half-yearly
Amount = ₹926.10
Rate per half-year = 10% ÷ 2
= 5%
Using:
A = P × (1 + R/100)^N
₹926.10 = ₹800 × (1 + 5/100)^N
₹926.10 ÷ ₹800 = (1.05)^N
1.157625 = (1.05)^N
Since:
1.157625 = (1.05)^3
Therefore:
N = 3 half-years
1 year = 2 half-years
Therefore:
3 half-years = 1.5 years
Answer: 1.5 years or 1 year 6 months
Question 8: An RRB Technician invests a certain sum from his salary at 12 1⁄2% compound interest per annum for 2 years. If the compound interest earned is ₹510, what will be the simple interest earned on the same sum at the same rate for the same period? (SSC)
Solution
Rate = 12½% per annum
Time = 2 years
Compound Interest = ₹510
First find the principal using:
CI = P × [(1 + R/100)^N − 1]
510 = P × [(1 + 12.5/100)^2 − 1]
510 = P × [(9/8)^2 − 1]
510 = P × (81/64 − 1)
510 = P × 17/64
P = 510 × 64 ÷ 17
P = ₹1,920
Now calculate Simple Interest:
SI = P × R × T ÷ 100
SI = 1,920 × 12.5 × 2 ÷ 100
SI = ₹480
Answer: ₹480
Question 9: A bank employee invests ₹12,000 in a scheme offering compound interest. The investment doubles in value every 5 years. What will be the value of the investment after 20 years? (SSC )
Solution
Principal = ₹12,000
The amount doubles in 5 years.
Therefore, amount after 5 years = ₹24,000.
Using our compound interest formula:
A = P × (1 + R/100)ⁿ
24,000 = 12,000 × (1 + R/100)⁵
Therefore:
(1 + R/100)⁵ = 2
Now, for 20 years:
A = 12,000 × (1 + R/100)²⁰
Since 20 = 5 × 4:
A = 12,000 × [(1 + R/100)⁵]⁴
A = 12,000 × 2⁴
A = 12,000 × 16
A = ₹1,92,000
Answer: ₹1,92,000
Quick Shortcut for SSC, RRB, Defence, Banking and Police Exams
The amount doubles every 5 years.
20 years = 5 × 4
So the amount doubles 4 times:
Final Amount = ₹12,000 × 2⁴
= ₹12,000 × 16
= ₹1,92,000
Answer: ₹1,92,000
Question 10: A bank employee invests a certain sum in a fixed deposit that earns 8% compound interest per annum, compounded quarterly. After 6 months, the investment grew to ₹26,010. What was the initial amount invested? (Bank)
Solution
Amount = ₹26,010
Rate = 8% per annum
Time = 6 months
Compounding = Quarterly
Rate per quarter:
8% ÷ 4 = 2%
Number of quarters in 6 months:
6 ÷ 3 = 2 quarters
Using:
A = P × (1 + R/100)ⁿ
26,010 = P × (1 + 2/100)²
26,010 = P × (1.02)²
26,010 = P × 1.0404
P = 26,010 ÷ 1.0404
P = ₹25,000
Answer: ₹25,000
Quick Shortcut
Rate per quarter = 8% ÷ 4 = 2%
6 months = 2 quarters
Therefore:
Principal = 26,010 ÷ (1.02)²
= 26,010 ÷ 1.0404
= ₹25,000
Answer: ₹25,000
Question 11: A bank employee lends a certain sum of money at simple interest. The amount becomes ₹720 after 2 years and ₹1,020 after a further 5 years. What was the original sum lent? (SSC)
(a) ₹500
(b) ₹600
(c) ₹700
(d) ₹710
Solution
Amount after 2 years = ₹720
Amount after 7 years = ₹1,020
Using:
SI = P × R × T ÷ 100
The additional interest for 5 years is:
₹1,020 − ₹720 = ₹300
So:
P × R × 5 ÷ 100 = 300
Therefore:
P × R = 6,000
For 2 years:
SI = P × R × 2 ÷ 100
= 6,000 × 2 ÷ 100
= ₹120
Now:
Amount = Principal + SI
₹720 = P + ₹120
P = ₹600
Quick Shortcut for SSC, RRB, Defence, Banking, and Police Exams
Increase in amount over 5 years:
₹1,020 − ₹720 = ₹300
So interest per year:
₹300 ÷ 5 = ₹60
Interest for first 2 years:
₹60 × 2 = ₹120
Therefore:
Principal = ₹720 − ₹120 = ₹600
Answer: ₹600
Question 12: An Assistant Section Officer (ASO) invests ₹150 from his first salary at 8% simple interest per annum. For how many years will it earn the same amount of interest as ₹800 invested at 4 1⁄2% simple interest per annum for 3 years?
(a) 6 years
(b) 8 years
(c) 9 years
(d) 12 years
Solution
Using the Simple Interest formula:
SI = P × R × T ÷ 100
For ₹150 at 8% per annum for T years:
SI = 150 × 8 × T ÷ 100
SI = 12T
For ₹800 at 4½% per annum for 3 years:
SI = 800 × 4.5 × 3 ÷ 100
SI = ₹108
Since the interests are equal:
12T = 108
T = 108 ÷ 12
T = 9 years
Answer: 9 years
Question 13: An RRB Technician has to purchase equipment for his work. If the equipment depreciates at the rate of 20% per annum, its value after 3 years will be less by what percentage of its original value? (RRB ALP)
(a) 45%
(b) 48.8%
(c) 51.2%
(d) 60%
Solution
Assume the original value of the equipment = ₹100
Depreciation = 20% per annum
Time = 3 years
Using our compound depreciation formula:
Final Value = Initial Value × (1 − R/100)ⁿ
Final Value = 100 × (1 − 20/100)³
= 100 × (0.8)³
= 100 × 0.512
= ₹51.20
Therefore, decrease in value:
₹100 − ₹51.20 = ₹48.80
So, the value will be less by 48.8%.
Answer: 48.8%
Question 14: The number of students enrolled in a government competitive-exam coaching institute is currently 10,000. The enrollment is expected to increase to 13,310 over the next 3 years at a uniform annual compound growth rate. What is the annual rate of growth?
(a) 8%
(b) 10%
(c) 12.7%
(d) 15%
Solution
Initial population = 10,000
Population after 3 years = 13,310
Time = 3 years
Using our compound growth formula:
A = P × (1 + R/100)ⁿ
13,310 = 10,000 × (1 + R/100)³
13,310 ÷ 10,000 = (1 + R/100)³
1.331 = (1 + R/100)³
Since:
1.1³ = 1.331
Therefore:
1 + R/100 = 1.1
R/100 = 0.1
R = 10%
Answer: 10%
Related Topics
Simple Interest & Compound Interest PYQ Analysis
These 14 previous year questions cover the major Simple Interest and Compound Interest concepts asked in SSC, RRB, Banking, Defence, and other competitive exams.
Difficulty Level
- Easy: 8 Questions
- Medium: 5 Questions
- Difficult: 1 Question
Key Topics Covered
- Simple Interest & Compound Interest
- Principal, Rate & Time
- Difference between CI & SI
- Half-Yearly & Quarterly Compounding
- Different Rates
- Equal Instalments
- Doubling & Compound Growth
- Equal Interest
- Compound Depreciation
Exam Insight
Most SI & CI questions test core formula application with a small twist. Identifying the question type and using the right formula or shortcut is the key to solving them quickly.
What You Should Learn From These PYQs
After solving these questions, you should be able to:
- Apply SI and CI formulas confidently.
- Find Principal, Rate, Time and Amount.
- Handle different compounding frequencies and rates.
- Solve CI–SI, installment, growth and depreciation problems.
- Use shortcuts to improve speed and accuracy.
If you can solve these 14 PYQs accurately, you will have covered the major SI & CI question types commonly asked in competitive examinations.
Resources Related to Simple Interest & Compound Interest PYQs
- Simple Interest & Compound Interest
- Simple Interest & Compound Interest Practice Questions
- Simple Interest Questions with Answers and Solutions
- Compound Growth Questions with Answers and Solutions
- Compound Interest Questions with Answers and Solutions (15 Solved)
- Simple Interest & Compound Interest Formula with Examples and Explanations
- Depreciation Questions with Answers and Solutions
- Difference Between Simple Interest and Compound Interest Questions with Answers and Solutions
- Profit, Loss & Discount PYQs SSC, RRB, Banking & Defence Exams