Percentages & Percent Change Core Formulas Percent = (Part / Whole) × 100 Percent Change = ((New - Original) / Original) × 100 Key Concepts Percent increase: new = original × (1 + rate) Percent decrease: new = original × (1 - rate) Successive percents: multiply the factors, don't add percentages Common SAT Traps 20% increase then 20% decrease ≠ original (it's 96% of original) "What percent of A is B?" means B/A × 100 Tax/tip problems: multiply by (1 + tax rate)