Problem Solving
试题详情
题目：
In a stack of cards, 9 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 6/11. What is the number of cards in the stack?
选项:
A、10
B、11
C、12
D、15
E、18
答案:
C
