Problem Solving

试题详情

题目:

The membership of a committee consists of 3 English teachers, 4 Mathematics teachers, and 2 Social Studies teachers.  If 2 committee members are to be selected at random to write the committee's report, what is the probability that the two members selected will both be English teachers?

选项:

A、   2/3
B、   1/3
C、   2/9
D、   1/12
E、   1/24

答案:

D

提问:

这道怎么解?
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提问:

不是(C13+C23)/C29吗? 分子是三种老师选一个C13 乘以 3个英语老师选2个 C23
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