A percentage expresses a number as parts per hundred. 45% means 45 out of 100, or 0.45 as a decimal, or 9/20 as a fraction. The symbol % evolved from the Italian "per cento."

Percentages make comparisons easy. A 10% discount, a 5% interest rate, a 20% increase—these are clear without knowing the base amount. Converting between percentages, decimals, and fractions is a basic skill. To find 15% of 80, multiply 80 by 0.15 to get 12.

Percentages appear in finance, statistics, science, and everyday life. Percentage change measures growth or decline. Percentage points distinguish absolute differences from relative ones. Misusing percentages can mislead, so understanding them is a form of numerical literacy.

• Ratio out of 100
• Convert to decimal by dividing by 100
• Used for discounts, interest, and changes
• Percentage points measure absolute difference