 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2019/paper-1/16/b/i/solution

For sampling without replacement, sum the two outcomes with a blue second draw:

P (B_{2}) = \frac{1}{10} + \frac{3}{10} = \frac{2}{5} (r = 0) .

The marginal blue probability equals the initial blue fraction even though the two draws are dependent.

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