Percentage Calculator Modes: Discounts, Marks, and Increase/Decrease
2026-05-09
When to use which percentage formula: finding X% of Y, change between two values, and common exam or pricing mistakes.
Percent of a number answers “what is 15% of 200?”—multiply the base by the percent over 100.
Percent change compares old and new values: (new − old) / old × 100, useful for price hikes and growth rates.
Discount math is easy to flip: 20% off is not the same as paying 20% of the original unless you define the base clearly.
Use one consistent mode per problem and label whether the percentage is of the original, the final, or the difference.