If you’re preparing for competitive exams like SSC CGL/CHSL, Railway, Banking, WBCS, UPSC, or State PSCs, mastering the Percentage chapter is essential. This is one of the most scoring and time-saving topics in the quantitative aptitude section.
In this blog, you’ll find the most useful percentage formulas, tricks, and examples to help you solve questions faster.
✅ Why Learn Percentage?
Because it appears in many chapters like:
Profit and Loss
Discount
Interest (SI/CI)
Data Interpretation
Ratio & Proportion
📘 Basic Percentage Formulas
1. Percentage Formula
Percentage = (Value / Total Value) × 100
2. Convert Percentage to Fraction
Divide the percentage by 100
Example: 25% = 25/100 = 1/4
3. Convert Fraction to Percentage
Multiply the fraction by 100
Example: 2/5 = (2 × 100)/5 = 40%
📘 Increase & Decrease Formulas
4. Percentage Increase Formula
Increase % = [(New Value – Original Value) / Original Value] × 100
5. Percentage Decrease Formula
Decrease % = [(Original Value – New Value) / Original Value] × 100
📘 Comparison Between Two Numbers
6. If A is x% more than B
Then B is (x / (100 + x)) × 100 % less than A
Example: If A is 25% more than B, then B is (25/125) × 100 = 20% less than A
7. If A is x% less than B
Then B is (x / (100 – x)) × 100 % more than A
Example: If A is 20% less than B, then B is (20/80) × 100 = 25% more than A
📘 Successive Percentage Change
When two percentage changes happen one after the other:
Net % Change = x + y + (x × y)/100
Use minus sign if it’s a decrease
Example: A value increases by 20% and then decreases by 10%
Net change = 20 – 10 + (20 × -10)/100 = 10 – 2 = 8% increase
📘 Percentage of a Quantity
8. x is what percent of y?
Formula: (x / y) × 100
Example: 30 is what percent of 120?
(30 / 120) × 100 = 25%
🧠 Shortcut Tricks to Remember
1/2 = 50%
1/3 = 33.33%
1/4 = 25%
1/5 = 20%
3/4 = 75%
These help in fast calculations during exams.
🔍 Sample Questions with Answers
Q1) 40% of a number is 120. What is the number?
Let the number be x
(40/100) × x = 120
⇒ x = (120 × 100)/40 = 300 ✅
Q2) A number is increased by 20% and then decreased by 20%. What is the final percentage change?
Using successive % formula:
= 20 – 20 + (20 × -20)/100 = 0 – 4 = 4% decrease ✅
🎯 Final Words
Learning percentage formulas can save time and boost your score in exams like SSC, Banking, WBCS, Railways, etc. Practice these daily and solve previous year questions for better results.
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