Question

有12（ A B C D E F G H I J K L )个同学,分在三个组里,每个组分4个同学,A B 分在同一组概

Answer 1

全部分法有C(12,4)*C(8,4)*C(4,4)种.

AB分在同一组的分法有C(10,2)*C(8,4)*C(4,4)种.

AB分在同一组的概率是[C(10,2)*C(8,4)*C(4,4)]/[C(12,4)*C(8,4)*C(4,4)]=C(10,2)/C(12.4)=1/11