A percentage is a number or ratio expressed as a fraction of 100. The word percentage comes from the Latin 'per centum', meaning 'per hundred'. For example, 45% means 45 per 100, or 45/100 = 0.45.

1. Basic Percentage (X% of Y): Calculates a percentage of a number. Example: 15% of 200 = 30
2. Percentage Change: Measures the relative change between old and new values. Formula: ((New - Original) / Original) × 100
3. Reverse Percentage: Finds what percentage one number is of another. Formula: (Part / Total) × 100

• Discounts and Sales: Calculate price reductions
• Academic Scores: Grade calculations and percentiles
• Financial Analysis: Interest rates, profit margins, growth rates
• Statistics: Population changes, market share
• Personal Finance: Tax rates, investment returns, savings goals

• To convert a percentage to a decimal, divide by 100 (e.g., 15% = 0.15)
• To convert a decimal to a percentage, multiply by 100 (e.g., 0.45 = 45%)
• In percentage change calculations, an increase shows a positive percentage, while a decrease shows a negative percentage
• When calculating discounts, subtract the percentage from 100% to find the final price percentage

1. Sales Tax: If an item costs $50 and sales tax is 8%, multiply $50 × 0.08 = $4 tax
2. Discount: A $80 item with 25% off: $80 × 0.25 = $20 discount, final price $60
3. Grade: Scoring 85 points out of 100 = 85%
4. Population Growth: If a city grows from 100,000 to 150,000 people, the growth is 50%