A box contains 6 white balls and 4 black balls. Three balls are drawn at random without replacement. What is the probability that all three are white?
Answer and explanation
Correct answer: B. 1/6
- Step 1: Total balls = 10. Number of ways to choose 3 white: C(6, 3) = (6 5 4) / 6 = 20. Step 2. Total ways to choose 3 balls from 10: C(10, 3) = (10 9 8) / 6 = 120. Step 3. Probability: 20 / 120 = 1/6. Answer: 1/6. Why not the others: 3/10 uses single-ball probability; 1/5 uses replacement. 1/12 does not fit.
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