1 - (1/30 + x) = 29/30 - xWe have also been told that the probability of false alarm is 10x. Hence the probability of real alarm is 1/30 = 10x. But this is equal to 3x since 3 times as many sharks are detected as go undetected

1/30 - 10x = 3xHence x = 1/390

Thus the probability of a peaceful day is

29/30 - 1/390 = 0.964

Source: Berrondom, Marie

Categories: Probability, Reasoning

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