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CUET · MATHS · PYQ PAPER 2025

Let box I contains 3 black and 4 white balls, box II contains 2 black and 2 white balls, box III contains 4 black and 3 white balls. A. box is selected at random and then a ball is randomly drawn from the selected box. If the color of the ball is black, then the probability that the ball is drawn from box III, is:

  1. A \(\frac{1}{7}\)
  2. B \(\frac{4}{21}\)
  3. C \(\frac{8}{21}\)
  4. D \(\frac{9}{21}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\frac{8}{21}\)

Step-by-step Solution

Detailed explanation

\( P(B|I) = \frac{3}{7} \), \( P(B|II) = \frac{2}{4} = \frac{1}{2} \), \( P(B|III) = \frac{4}{7} \) \( P(I) = P(II) = P(III) = \frac{1}{3} \) \( P(B) = P(B|I)P(I) + P(B|II)P(II) + P(B|III)P(III) \)…
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