Mathematics
Weighted Average
Calculate average when different groups have different sizes.
Weighted Average = (n₁x₁ + n₂x₂) / (n₁ + n₂)
Formula Explanation
Each value is multiplied by its frequency or weight before averaging.
Variables Explained
n₁, n₂ = frequencies; x₁, x₂ = values.
Solved Example
Class A (20 students) average 70, Class B (30 students) average 80. Combined average?
(20×70 + 30×80)/50 = 76.