TS EAMCET · Maths · Probability
There are two boxes each containing 10 balls. In each box, few of them are black balls and rest are white. A ball is drawn at random from one of the boxes and found that it is black. If the probability that the black ball drawn is from the second box is \(\frac{1}{5}\), then number of black balls in the first box is
- A 5 or 10
- B 2 or 7
- C 4 or 8
- D 3 or 6 or 9
Answer & Solution
Correct Answer
(C) 4 or 8
Step-by-step Solution
Detailed explanation
\(P(Box_2|B) = \frac{P(B|Box_2)P(Box_2)}{P(B|Box_1)P(Box_1) + P(B|Box_2)P(Box_2)}\) \(\frac{1}{5} = \frac{\left(\frac{n_2}{10}\right)\left(\frac{1}{2}\right)}{\left(\frac{n_1}{10}\right)\left(\frac{1}{2}\right) + \left(\frac{n_2}{10}\right)\left(\frac{1}{2}\right)}\)…
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