NDA 2024 · PYQ · Probability / Combinations · easy
A bag contains 5 black and 4 white balls. A man selects two balls at random. What is the probability that both of these are of the same colour?
A.1/6
B.5/108
C.4/9✓ Correct
D.5/18
Explanation
Total ways to select 2 balls from 9 = C(9,2) = 36. Ways to select 2 black balls from 5 = C(5,2) = 10. Ways to select 2 white balls from 4 = C(4,2) = 6. Favourable outcomes = 10 + 6 = 16. Probability = 16/36 = 4/9.
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