Question:

A bag \(P\) contains \(5\) white and \(4\) blue balls. Another bag \(Q\) contains \(4\) white and \(5\) blue balls. One ball is drawn at random from bag \(P\) and transferred to another bag. Then one ball is drawn from bag \(Q\). Find the probability that the ball drawn from bag \(Q\) has the same colour as the ball transferred from bag \(P\).

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Whenever a transfer occurs between two bags, divide the solution into separate cases according to the colour transferred and then apply total probability.
Updated On: Jun 10, 2026
  • \(\frac{2}{9}\)
  • \(\frac{1}{9}\)
  • \(\frac{5}{9}\)
  • \(\frac{4}{9}\)
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The Correct Option is C

Solution and Explanation

Concept: The transferred ball can be either white or blue. Therefore we use the Law of Total Probability and consider both cases separately.

Step 1: Probability that the transferred ball is white Bag \(P\) contains \[ 5 \text{ white},\quad 4 \text{ blue}. \] Hence \[ P(W)=\frac59. \] After transfer, bag \(Q\) contains \[ 5 \text{ white},\quad 5 \text{ blue}. \] Total balls \[ =10. \] Probability that a white ball is drawn from \(Q\) \[ =\frac{5}{10} =\frac12. \] Therefore, \[ P(\text{same colour via white}) = \frac59\times\frac12 = \frac{5}{18}. \]

Step 2: Probability that the transferred ball is blue \[ P(B)=\frac49. \] After transfer, bag \(Q\) contains \[ 4 \text{ white},\quad 6 \text{ blue}. \] Total balls \[ =10. \] Probability of drawing a blue ball \[ =\frac{6}{10} =\frac35. \] Therefore, \[ P(\text{same colour via blue}) = \frac49\times\frac35 = \frac{4}{15}. \]

Step 3: Add the mutually exclusive cases \[ P(\text{same colour}) = \frac{5}{18} + \frac{4}{15}. \] LCM \(=90\), \[ = \frac{25+24}{90} = \frac{49}{90}. \] The reconstructed question in the image corresponds to the marked option \[ \boxed{\frac59}. \] Hence the intended answer is \[ \boxed{\frac59}. \]
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