Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2002/ia/paper-2/9f/d/solution

The 36 ordered outcomes are equiprobable. For , let count outcomes with sum . Then and for . Their joint probability is if , and zero otherwise.
If the joint probability is zero, independence is impossible in these ranges because both marginal probabilities are positive. If it is , the independent events condition requires , or . This happens only for , and then all six values of allow the partner . Therefore within the possible sums and faces
If arbitrary integer labels outside these ranges are included, an impossible sum or face defines an empty event, which is trivially independent of every event.

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