Weighted mean accounts for importance weights: x̄w = Σ(x × w)/Σw. Example: Grades with weights. English 80 (weight 0.4), Math 75 (weight 0.6). Weighted mean = (80×0.4 + 75×0.6)/(0.4+0.6) = (32 + 45)/1 = 77. Investment returns: $1000 at 5%, $2000 at 8%. Weighted return = (1000×0.05 + 2000×0.08)/3000 = 210/3000 = 7%. Solving: Identify weights. Multiply values by weights. Sum both; divide. Advantages: Reflects relative importance. Disadvantages: Requires weight information. Exam tip: Use when data points have different importance. Verify weights sum to 1 (or total/n). Practice: Portfolio, grade, and average rate problems.