Percentatges

Percentatges, commonly known as percentages, express a portion of a whole as parts per hundred. A percentage is written with the symbol % and represents the fraction divided by 100. For example, 25% equals 25/100 or 0.25.

Converting between percents, decimals, and fractions: to convert a percentage to a decimal, divide by 100; to convert a decimal to a percentage, multiply by 100 and append %; to convert a fraction a/b to a percentage, multiply by 100%.

Percentages are used to describe portions of discrete quantities and to calculate amounts. x% of y equals y × x/100. Percentage change from a base value uses the formula new value = old value × (1 + rate) for increases or (1 − rate) for decreases, where rate is expressed as a decimal (e.g., 20% = 0.20).

Examples: 40% of 250 is 100; a 15% discount on a price of 80 reduces it to 68 (80 × 0.85).

Common contexts include finance (interest, discounts, taxation), statistics (survey results, sampling error), demographics, and quality control. Percentages are often used in charts and tables to summarize data.

Rounding and base selection can affect interpretation. A percentage describes a relation to a specified whole; comparing percentages without specifying the base can be misleading.

Historically, percent notation emerged in commerce and mathematics; today the percent symbol % is widely used in mathematics and everyday life.