JEE Mains · Maths · STD 12 - 13. probability
A bag contains \(8\) balls, whose colours are either white or black. \(4\) balls are drawn at random without replacement and it was found that \(2\) balls are white and other \(2\) balls are black. The probability that the bag contains equal number of white and black balls is :
- A \(\frac{2}{5}\)
- B \(\frac{2}{7}\)
- C \(\frac{1}{7}\)
- D \(\frac{1}{5}\)
Answer & Solution
Correct Answer
(B) \(\frac{2}{7}\)
Step-by-step Solution
Detailed explanation
\( \mathrm{P}(4 \mathrm{~W} 4 \mathrm{~B} / 2 \mathrm{~W} 2 \mathrm{~B})=\) \( \frac{P(4 W 4 B) \times P(2 W 2 B / 4 W 4 B)}{P(2 W 6 B) \times P(2 W 2 B / 2 W 6 B)+P(3 W 5 B) \times P(2 W 2 B / 3 W 5 B)} +\ldots \ldots \ldots+P(6 W 2 B) \times P(2 W 2 B / 6 W 2 B)\)…
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