Understanding Percentages

A percentage represents a part of a whole, expressed as a fraction of 100. The term comes from the Latin 'per centum' meaning 'by the hundred'.

Common Percentage Calculations

Finding a Percentage

To find what percentage X is of Y, divide X by Y and multiply by 100. Example: 50 is what % of 200? (50 ÷ 200) × 100 = 25%

Finding a Value

To find what number is X% of Y, multiply Y by X/100. Example: What is 25% of 200? 200 × (25 ÷ 100) = 50

Percentage Change

To find the percentage increase/decrease, subtract old from new, divide by old value, and multiply by 100.

Real-World Applications

• Discounts and sales
• Tax calculations
• Interest rates
• Statistical analysis
• Grade calculations
• Population changes

Tips for Working with Percentages

• Convert percentage to decimal by dividing by 100
• To add a percentage, multiply by (1 + percentage/100)
• To subtract a percentage, multiply by (1 - percentage/100)
• Remember that percent means "per hundred"
• Use benchmarks like 50% (half) and 25% (quarter) for estimation