Problem Solving and Logical Thinking Practice
Simple & Compound Interest – Shortcut Tricks & Tough Problems
Interest is a key topic in bank exams. Understanding concepts and shortcuts helps solve quickly.
1. Simple Interest (SI)
Formula:
SI = (P × R × T) ÷ 100
P = Principal, R = Rate, T = Time
Example:
P = 1000, R = 10%, T = 2 years
SI = (1000×10×2)/100 = 200
2. Compound Interest (CI)
Formula:
Amount = P(1 + R/100)^T
CI = Amount - Principal
Example:
P = 1000, R = 10%, T = 2 years
Amount = 1000(1.1)^2 = 1210
CI = 210
3. Shortcut for 2 Years
CI - SI = P × (R/100)^2
Example:
P = 1000, R = 10%
Difference = 1000 × (0.1)^2 = 10
4. Growth Concept
For increase:
Multiply by (1 + rate)
For decrease:
Multiply by (1 - rate)
Tough Problems
Q1:
Find SI on 2000 at 5% for 3 years.
Solution:
SI = (2000×5×3)/100 = 300
Q2:
Find CI on 1000 at 10% for 2 years.
Solution:
Amount = 1000(1.1)^2 = 1210
CI = 210
Q3:
Find difference between CI and SI on 5000 at 10% for 2 years.
Solution:
Difference = 5000 × (0.1)^2 = 50
Exam Strategy
- Use SI formula directly
- Use shortcut for CI (2 years)
- Avoid full power calculation if shortcut available
- Focus on difference questions
Quantitative Aptitude • Bank Exams • Competitive Preparation
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