In a sample of 10 cards, 4 are red and 6 are blue. If 2 cards are selected at random from the sample, one at a time without replacement, what is the probability that both cards are not blue?
- A
- B
- C
- D
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Correct answer: A
The probability that both cards are not blue is the same as the probability that both cards are red. There are 4 red cards out of the 10, so the probability of the first card being red is
Now there are 9 cards left, and 3 of those are red, so the probability of the second card being red is
Multiply the two probabilities to find the probability that both cards are red (not blue):