What is Percentage?
Percentage means "per hundred." It expresses a number as a fraction of 100. Formula: Percentage = (Part / Whole) × 100. Example: 25 out of 200 = (25/200) × 100 = 12.5%
Common Percentage Formulas
- X% of Y: Y × X / 100
- Percentage Change: (New – Old) / Old × 100
- Percentage Increase: Value × (1 + X/100)
- Percentage Decrease: Value × (1 – X/100)
- Reverse Percentage: Final / (1 + X/100)
Quick Mental Math Tricks
- 10% of anything: move decimal point left once
- 5% = half of 10%
- 15% = 10% + 5%
- 20% = 10% × 2, or divide by 5
- 25% = divide by 4
Percentage in Daily Life
Discounts (30% off ₹2,000 = ₹1,400), tax calculations (18% GST), exam scores (85/100 = 85%), interest rates (FD at 7%), salary hikes (10% raise), and more. Understanding percentages is essential for financial literacy.
Common Mistakes to Avoid
- Confusing percentage points with percentages (8% to 10% is a 2 percentage point increase, but 25% increase)
- Successive percentages don't simply add (10% + 10% ≠ 20%; it's 21%)
- Percentage decrease then same increase doesn't return to original