In a stack of cards, 6 cards are blue and the rest are red. If 2 cards are to be chosen at random from the stack without replacement, the probability that the cards chosen will both be blue is 8/11. What is the number of cards in the stack? Choose the correct choice from the following answers:
A) 7  B) 11  C) 12  D) 15  E) 18
This question can be solved by TESTing THE ANSWERS.   We're told that we have 6 blue cards and an unknown number of red cards. We're also told that if 2 cards are to be chosen at random from the stack WITHOUT replacement, then the probability that the cards chosen will BOTH be BLUE is 8/11. We're asked for the TOTAL number of cards.   Probability of pulling two blue cards is...   (6/7)(5/6) = 30/42~ 8/11   7
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In a stack of cards, 6 cards are blue and the rest are red. If 2 cards are to be chosen at random from the stack without replacement, the probability that the cards chosen will both be blue is 8/11. What is the number of cards in the stack?