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Question
A bag contains 8 red, 3 white and 9 blue balls. If three balls are drawn at random, determine the probability that all the three balls are blue balls
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Solution
Out of 20 balls, three balls can be drawn in 20C3 ways.
∴ Total number of elementary events = 20C3
Out of nine blue balls, three blue balls can be chosen in 9C3 ways.
∴ Favourable number of events = 9C3 ways.
Hence, required probability = \[\frac{^{9}{}{C}_3}{^{20}{}{C}_3} = \frac{9 \times 8 \times 7}{20 \times 19 \times 18} = \frac{7}{95}\]
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