Percent Change
% change = (new − old) / old × 100
Fraction ↔ Decimal
1/2=0.5 | 1/3≈0.33 | 1/4=0.25 | 1/5=0.2 | 1/8=0.125
Ratios
Part/Whole = fraction; cross-multiply to solve proportions
Percent of a Number
x% of N = (x/100) × N | 10% shortcut: move decimal left
Quick Tips
To find 15%, find 10% + 5% (half of 10%)
