GWD-7-14

renprince

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

qwrersaa

1-6号6个卡片。随机抽一个然后放回，再抽一张，两张数字和是8，问其中有一张是5的概率。

可能是2+6,6+2,5+3,3+5,4+4这5种可能

因为已知两张和是8，而只有这5种可能，这5种可能的概率相等，里面有2种情况含有5

所以是2/5选D

renprince

明白了，谢谢楼主！！！