There are six cards each with a number from 1 to 6. Draw one card randomly and then put it back into a bowl. If one card is to be drawn randomly, and the sum of two cards is 8, what’s the probability that the card is 5?
【答案】2/5
【思路】因放回，两张cards之和＝8有5种可能，2 6，6 2，3 5，5 3，4 4，其中出现5的可能有2种。
题目中the card是指得第一张卡还是第一张或者二张？我怎么觉得是值得第二张 | 
