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FRM Part I · FRM Exam Part I · Fundamentals of Probability

A trader has two independent strategies. Strategy X profits on a given day with probability 0.60 and strategy Y with probability 0.50. Given that exactly one strategy profits on a day, what is the probability that it is strategy X?

The probability is 0.60. X profits alone with probability 0.30 and Y profits alone with probability 0.20, so exactly one profits with probability 0.50. Dividing 0.30 by 0.50 gives 0.60, matching option 0.600 rather than 0.545 or 0.300.

  1. A0.600
  2. B0.500
  3. C0.545Correct
  4. D0.300

Explanation

P(X only) = 0.60 x 0.50 = 0.30. P(Y only) = 0.40 x 0.50 = 0.20. P(exactly one) = 0.50. P(X | exactly one) = 0.30/0.50 = 0.60. So the correct value is 0.600.

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