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Two boxes A and B contain white and black balls. Box A contains 4 black and 5 white balls, while box B contains 3 black and 4 white balls. One of the balls is randomly drawn from one of the two boxes. Find the probability of the ball being drawn from box A if it is known that it is a white ball?
  • a)
    20/63
  • b)
    35/71
  • c)
    43/63
  • d)
    36/71
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
Two boxes A and B contain white and black balls. Box A contains 4 bla...
Probability of choosing either of the boxes = ½
The probability of drawing a white ball from box A = 1/2 x 5/9 = 5/18
The probability of drawing a white ball from box B = 1/2 × 4/7 = 2/7
The probability of drawing a white ball = 5/18 + 2/7 = 35+36/126 = 71/126
It is given that the ball drawn was white.
Hence the probability that the white ball was drawn from box A = 5/18/71/126 = 35/71
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Most Upvoted Answer
Two boxes A and B contain white and black balls. Box A contains 4 bla...
To find the probability of drawing a white ball from box A, we need to use Bayes' theorem. Bayes' theorem states that the probability of an event A occurring given that event B has occurred is equal to the probability of event B occurring given that event A has occurred, multiplied by the probability of event A occurring, divided by the probability of event B occurring.

Let's denote the events as follows:
A: Drawing a white ball from box A
B: Drawing a white ball

We are given the following information:
P(A) = probability of drawing a white ball from box A = 5/9
P(B|A) = probability of drawing a white ball given that it is from box A = 5/9
P(B) = probability of drawing a white ball = ?

To find P(B), we need to consider the probabilities of drawing a white ball from both boxes.

P(B) = P(B|A) * P(A) + P(B|B) * P(B)

P(B|B) = probability of drawing a white ball given that it is from box B = 4/7
P(B|A) = probability of drawing a white ball given that it is from box A = 5/9

Now we can substitute the values into the equation:

P(B) = (5/9) * (5/9) + (4/7) * (4/9)
= 25/81 + 16/63
= (25 * 7 + 16 * 9) / (81 * 7)
= (175 + 144) / 567
= 319 / 567

Simplifying the fraction, we get:

P(B) = 319 / 567 = 35/71

Therefore, the probability of drawing a white ball from box A, given that it is a white ball, is 35/71.
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Two boxes A and B contain white and black balls. Box A contains 4 black and 5 white balls, while box B contains 3 black and 4 white balls. One of the balls is randomly drawn from one of the two boxes. Find the probability of the ball being drawn from box A if it is known that it is a white ball?a)20/63b)35/71c)43/63d)36/71e)None of theseCorrect answer is option 'B'. Can you explain this answer?
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