|
- 精华
- 0
- 积分
- 107
- 经验
- 107 点
- 威望
- 0 点
- 金钱
- 190 ￥
- 魅力
- 107
|
请教一道排列组合题
请教一道排列组合题:
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
答案是D, 请哪位指点如何得出？多谢！
|
|
