(c) 13
Using the empirical relationship: Mode = 3 Median − 2 Mean = 3(11) − 2(10) = 33 − 20 = 13.
Source: Chapter 13, Section 13.4 (Remarks)
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The key formula to remember is the empirical relationship between the three measures of central tendency:
Mode = 3 Median − 2 Mean
This is stated in the Remarks under Section 13.4. Simply substitute Mean = 10 and Median = 11 to get Mode = 33 − 20 = 13. Examiners expect you to recall and apply this formula directly for such 1-mark questions.