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Arithmetic Formulas
Percent, ratios, averages, and basics. · 7 formulas
Percentage
P% of N = (P/100) × NPart = percent × whole
Example
16
Percent Increase / Decrease
% = ((new−old)/old) × 100Change relative to original
Example
20% increase
Ratio
a : b = a/bCompare two quantities
Example
3 : 2
Average (Mean)
Mean = Sum / CountAdd all values, divide by how many
Example
6
Proportion
a/b = c/d → a×d = b×cCross-multiply equal ratios
Example
x = 9
Fraction of a Number
(a/b) × NMultiply the number by the fraction
Example
15
Unit Rate
rate = quantity ÷ unitsAmount per one unit
Example
60 km/h