Why are Percentages Important?
Percentages are everywhere in daily life—from figuring out a tip at a restaurant to understanding a store discount, calculating sales tax, and measuring your stock portfolio's growth. The word "percent" literally means "per hundred" in Latin.
Common Percentage Formulas
1. What is X% of Y?
Result = (X ÷ 100) × Y
Example: What is 20% of 150?
(20 ÷ 100) × 150 = 0.20 × 150 = 30.
2. X is what percent of Y?
Result = (X ÷ Y) × 100
Example: 30 is what percent of 150?
(30 ÷ 150) × 100 = 0.20 × 100 = 20%.
3. Percentage Change (Increase/Decrease)
Result = ((New Value - Old Value) ÷ Old Value) × 100
Example: What is the percentage change from 100 to 150?
((150 - 100) ÷ 100) × 100 = (50 ÷ 100) × 100 = 50% Increase.