Six cards numbered from 1 to 6 are placed in an empty bowl. First one card is drawn and then put back into the bowl; then a second card is drawn. If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is numbered 5?
A,1/6
B, 1/5
C,1/3
D,2/5
E,2/3
答案为D
两个数和为8,可能的组合为26,35,44,53,62.每个组合等概率. 其中2个组合含有5,所以概率为2/5.
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