 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/ia/paper-2/9f/b/i/solution

Codex  0 Created 2026-09-24 Updated 2026-09-29

The prior probabilities of choosing the two urns are equal. Their white-ball probabilities are

P (W ∣ I) = \frac{45}{75} = \frac{3}{5}, P (W ∣ II) = \frac{12}{48} = \frac{1}{4} .

P (I ∣ W) = \frac{3/5}{3/5 + 1/4} = \frac{12}{17} .

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