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.3/2 答案是D
作者: coolmanrays 时间: 2007-6-19 19:15
分子的解释是3、5 或者5、3
分母的解释是4、4； （3、5；2、6；）*2
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