Multiple choice

A bag contains 5 red discs and 4 blue discs. If 3 discs are drawn from the bag without replacement, find the probability that all three are blue.

  1. 1/21

  2. 2/21

  3. 1/7

  4. 4/21
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A Correct answer
Explanation

Total discs = 9. The probability of drawing 3 blue discs without replacement is (4/9) * (3/8) * (2/7) = 24 / 504. Simplifying this fraction, 24 / 504 = 1 / 21.

AI explanation

Using the method of combinations, the total number of ways to draw 3 discs from 9 is 9C3 = 84. The number of ways to draw 3 blue discs from the 4 available is 4C3 = 4. The required probability is 4/84, which simplifies to 1/21.

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