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26 red and 26 black cards, 3 cards drawn without replacement, order doesn't matter.
  • Total ways to choose 3 out of 52 cards: 52C3
  • Case 1: 2 red, 1 black: 26C2*26C1
  • Case 2: 2 black, 1 red: 26C2*26C1
P: \(\frac{Case 1+2}{Total} = \frac{2*26C2*26C1}{52C3}\)
Answer: B
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avellanjc
Can someone please expand on the explanation of why for the favourable outcomes the pool from where to choose becomes 26 (and not 52).

Thanks in advance.

Regards,

Juan C. Avellan
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Both the colors cards can be drawn if there is one black and two red or one red and two black cards
So favorable outcomes = 26C1 x 26C2 + 26C2 x 26C1 = 2 x 26C1 x 26C2
Total Outcomes = 52C3

So the answer is B. 2 x 26C1 x 26C2/ 52C3
The total number of choices (the 'pool') depends on the context. 26 is the color pool, in this case red = black = 26. If you pick 2 out of 26 red cards, you have 26C2 ways to do it. Now those red cards are in a bigger pool: a deck of 52 cards, with the remaining 26 cards not red. Then the number of favorable outcomes (2 red cards) remains 26C2, but the total possible 2-card selection is 52C2; and the chance becomes 26C2/52C2.
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