Key Concepts
- Reverse percentage problems involve finding the original number before a percentage change.
- Formula: Original Value = New Value ÷ (1 ± percentage as a decimal).
- Example: If a price after a 20% increase is $120, the original price was $120 ÷ 1.2 = $100.
Skills Covered
- Determine the original value before a percentage increase/decrease.
- Solve problems where a given number is a percentage of another unknown number.
Example Problems
- A price after a 25% increase is $250. What was the original price?
- If 72 is 80% of a number, what is the original number?
- A product was sold for $90 after a 10% discount. What was the original price?