Out of 10 persons working on a project, 4 are graduates. If 3 are selected, what is the probability that there is at least one graduate among them?
Correct answer: D. 5/6Pakistan Studies Quiz
- A. 1/6
- B. 5/8
- C. 3/8
- D. 5/6Pakistan Studies Quiz
Explanation
Use the complement: the probability of selecting no graduate is C(6,3) ÷ C(10,3) = 20 ÷ 120 = 1/6, because 6 of the 10 people are non-graduates. Hence the probability of at least one graduate is 1 - 1/6 = 5/6. Students may choose 1/6 by reporting the probability of no graduate instead of its complement.
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