Weighted mean
A standard method from Measures of central tendency: the steps and worked examples.
Steps
Weighted mean = Σ(value × weight) ÷ Σ(weight).
Worked examples
Example 1: The mean of 5 numbers is 12. Four of them are 10, 11, 15 and 9. Find the fifth.
total = 12 × 5 = 60
fifth = 60 − (10 + 11 + 15 + 9) = 15For the whole topic, read Measures of central tendency: key points, common mistakes and how the DSE tests it.