Permutation & Combination Answers

Permutation and Combination - Quant/Math - CAT 2007

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Question 4 the day: November 18, 2003

The question for the day is from the topic Permutation and Combination.

Question:

Badri has 9 pairs of dark Blue socks and 9 pairs of Black socks. He keeps them all in a same bag. If he picks out three socks at random what is the probability he will get a matching pair?

(1) (2*⁹C₂ * ⁹C₁) / ¹⁸C₃
(2) (⁹C₂ * ⁹C₁) / ¹⁸C₃
(3) 1
(4) None of these

Correct Answer - (3)

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Solution:


If he picks any of the three socks invariably any two of them should match. Hence the probability is 1.