Simple Interest and Compound Interest Formula Key Facts PYQ
📋 NOTES Guide
✅ Updated 2026
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Understanding the concepts of Simple Interest (SI) and Compound Interest (CI) is crucial for various competitive exams in India. This article provides key facts, formulas, and previous year questions (PYQ) related to these topics, helping aspirants prepare effectively.
Simple Interest Formula
SI = (P × R × T) / 100
Compound Interest Formula
CI = P(1 + R/100)^T - P
Core Formula Derivations
The derivations of the formulas for SI and CI are essential for understanding their applications:
- Simple Interest: Derived from the basic principle of interest being calculated on the principal amount.
- Compound Interest: Involves interest being calculated on the initial principal and also on the accumulated interest from previous periods.
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Difference Between SI and CI
| Aspect | Simple Interest | Compound Interest |
|---|---|---|
| Interest Calculation | On principal only | On principal + accumulated interest |
| Growth | Linear | Exponential |
Shortcut Tricks
A few shortcut tricks to remember:
- For SI, remember the formula as "Principal × Rate × Time".
- For CI, use the formula "P(1 + R/100)^T" to quickly calculate the total amount.
Common PYQ Patterns
Previous year questions often focus on:
- Calculating SI and CI for given values.
- Comparing the total amounts after a certain period.
Typical Mistakes
Common mistakes include:
- Forgetting to convert the rate into a decimal for CI calculations.
- Misunderstanding the time period in years versus months.
Exams That Ask About SI and CI
These concepts are frequently tested in:
- SSC CGL
- IBPS PO
- UPSC
Previous Year Questions (PYQ)
| Year | Question | Answer |
|---|---|---|
| 2022 | Calculate SI for ₹5000 at 5% for 3 years. | ₹750 |
| 2021 | Find CI for ₹1000 at 10% for 2 years. | ₹210 |
Practical Next Steps
To prepare effectively:
- Practice PYQs regularly to familiarize yourself with question patterns.
- Use online calculators to verify your manual calculations.
📌 Must Remember — Simple Interest and Compound Interest Formula Key Facts PYQ
1
SI = (P × R × T) / 100
2
CI = P(1 + R/100)^T - P
3
Common mistakes include rate conversion errors.
4
Practice PYQs for better preparation.
5
CI grows exponentially compared to SI.
6
Use online tools to verify calculations.
7
Focus on understanding the concepts deeply.
8
Review previous year questions regularly.
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