Simple and Compound Interest for RRB NTPC: Download Free PDF & Practice Now

Aiming for a Station Master or Goods Guard post in Indian Railways? The RRB NTPC exam is the biggest opportunity for you. But to grab that seat, you need to score good marks in the exam. In the Quantitative Aptitude section, there is one topic that appears in every single shift: Simple Interest (SI) and Compound Interest (CI). Many students get nervous when they see problems involving “Rates,” “Years,” and “Amount.” They think they need complex calculations. But here is the truth: In RRB NTPC, the examiner checks your logic, not your calculator speed. The questions are tricky but short. If you know the right approach, you can solve them in 30 seconds. To help you prepare smart, we have analyzed the last 5 years of Railway papers. In this blog, we have provided some exam-level questions of simple and compound interest for RRB NTPC that will help you boost your preparation.

Why is Simple & Compound Interest Important?

In both CBT-1 and CBT-2, this topic is a rank booster.

• High Weightage: You can expect 2 to 3 questions in CBT-1 and even more in CBT-2.
• Direct Formulas: Unlike Geometry, you don’t need to prove theorems. Just put the values in the formula.
• Repeated Patterns: Railway exams love specific types of questions, like “Find the difference between SI and CI for 2 years.” If you master just this one type, your marks are secured.

Understanding the Concept (In Simple Words)

• Simple Interest (SI): Think of this as a fixed rent. Whether it is the 1st year or the 10th year, the interest amount remains the same.
• Compound Interest (CI): This is “Interest on Interest.” If you earned ₹100 interest this year, next year you will earn interest on that ₹100 too. The money grows much faster here.

Download Free PDF of SI & CI Questions for RRB NTPC

We have prepared a comprehensive PDF containing exam-level questions. We have chosen questions that are not too easy and not too hard—just the perfect RRB NTPC level. Download it, save it, and practice these questions to build your speed.

Q1. Find the Simple Interest on ₹6000 at 8% per annum for 3 years.
(a) ₹1440
(b) ₹1200
(c) ₹1500
(d) ₹1600

Answer: (a) ₹1440

Logic:
SI = (P × R × T) / 100
= (6000 × 8 × 3) / 100
= ₹1440

Q2. At what rate percent per annum will a sum of money double itself in 8 years at Simple Interest?
(a) 10%
(b) 12.5%
(c) 15%
(d) 20%

Answer: (b) 12.5%

Logic:
To double, Interest = Principal
100 = (100 × R × 8) / 100
8R = 100
R = 12.5%

Q3. Find the Compound Interest on ₹5000 for 2 years at 10% per annum.
(a) ₹1000
(b) ₹1050
(c) ₹1100
(d) ₹1200

Answer: (b) ₹1050

Logic:
1st year interest = 10% of 5000 = 500
Amount after 1st year = 5500
2nd year interest = 10% of 5500 = 550
Total CI = 500 + 550 = ₹1050

Q4. The difference between CI and SI on a certain sum for 2 years at 10% per annum is ₹40. Find the sum.
(a) ₹2000
(b) ₹3000
(c) ₹4000
(d) ₹5000

Answer: (c) ₹4000

Logic:
Difference = P × (R/100)²
40 = P × (10/100)²
40 = P × (1/100)
P = ₹4000

Q5. In how many years will ₹4000 amount to ₹5200 at 6% Simple Interest?
(a) 3 years
(b) 4 years
(c) 5 years
(d) 6 years

Answer: (c) 5 years

Logic:
Interest = 5200 − 4000 = 1200
1200 = (4000 × 6 × T) / 100
1200 = 240T
T = 5 years

Q6. If a sum of money amounts to ₹21600 in 3 years at 20% Compound Interest, what is the Principal? (approx)
(a) ₹12000
(b) ₹12500
(c) ₹15000
(d) ₹10000

Answer: (b) ₹12500

Logic:
20% ⇒ 5 becomes 6
In 3 years: 5³ becomes 6³
125 becomes 216
Given amount = 21600
Principal = 125 × 100 = ₹12500

Q7. Simple Interest on a sum for 2 years at 4% is ₹80. Find the Compound Interest on the same sum for the same period.
(a) ₹81.60
(b) ₹82
(c) ₹80.80
(d) ₹85

Answer: (a) ₹81.60

Logic:
SI for 1 year = 80 / 2 = 40
Extra CI = 4% of 40 = 1.60
Total CI = 80 + 1.60 = ₹81.60

Q8. A sum becomes 2 times in 5 years at Simple Interest. In how many years will it become 4 times?
(a) 10 years
(b) 15 years
(c) 20 years
(d) 12 years

Answer: (b) 15 years

Logic:
To become 2 times ⇒ Interest = P in 5 years
To become 4 times ⇒ Interest = 3P
Time ∝ Interest
Required time = 5 × 3 = 15 years

Q9. Find the amount if ₹10,000 is invested at 20% per annum for 1.5 years, compounded half-yearly.
(a) ₹13,000
(b) ₹13,310
(c) ₹12,000
(d) ₹14,000

Answer: (b) ₹13,310

Logic:
Half-yearly ⇒ Rate = 10%, Time = 3 periods
Amount factor = (11/10)³ = 1331/1000
Amount = 10000 × 1331 / 1000 = ₹13,310

Q10. At what rate percent per annum will ₹1000 amount to ₹1331 in 3 years at Compound Interest?
(a) 8%
(b) 10%
(c) 12%
(d) 15%

Answer: (b) 10%

Logic:
1331 / 1000 = (11/10)³
Money grows from 10 to 11
Increase = 1 on 10
Rate = 10%

How to Prepare Interest Questions Easily?

Don’t let the calculations scare you. Follow these simple tips to master this topic:

• Memorize the “Difference” Formula: The question “Find the difference between SI and CI for 2 years” is a favorite of the Railway Board. Just remember: D=P(R/100)². It solves the problem in seconds.
• Use the “Fraction Method”: For Compound Interest, avoid the long formula. Convert % to fraction (e.g., 10%=1/10). It makes the calculation much faster.
• Watch Out for “Half-Yearly”: In RRB exams, they often trick you with “Compounded Half-Yearly.” Just remember: Rate becomes Half and Time becomes Double.
• Practice with Topic Tests: Reading is not enough. You must solve. Attempt our Free Topic Tests to increase your calculation speed.

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