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MathsJEE Main 28 Jan 2026, Shift 1·Q9·MCQ·Moderate

Probability · Bayes theorem

A bag contains 10 balls out of which kk are red and (10−k)(10 - k) are black, where 0≤k≤100 \le k \le 10. If three balls are drawn at random without replacement and all of them are found to be black, then the probability that the bag contains 1 red and 9 black balls is:
  1. (1)711\dfrac{7}{11}
  2. (2)755\dfrac{7}{55}
  3. (3)7110\dfrac{7}{110}
  4. (4)1455\dfrac{14}{55}
We corrected a printing error in the original paper

Source printed “the bag contains l red and 9 black balls” (letter l for the digit 1).

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