Probability Gmatclub tests

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by GMATGuruNY » Wed Feb 09, 2011 8:21 pm
achieve_dream wrote:There are six cards bearing numbers 2,4,5,5,5,6. If two cards are randomly selected from the lot, what is the probability that the difference between the numbers on these cards is 3 or less?

8/15
9/15
10/15
12/15
14/15
From the 6 cards, the number of combinations of 2 that can be chosen = 6C2 = 15.

Of these 15 combinations, only 1 combination (6,2) will result in a difference of more than 3:
6-2 = 4.

Thus, the remaining 15-1 = 14 combinations will yield a difference of 3 or less.

P(difference of 3 or less) = 14/15.

The correct answer is E.
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