问题 填空题

2位男生和3位女生共5位同学站成一排,若男生甲不站两端,3位女生中有且只有两位女生相邻,则不同排法的种数是______.

答案

从3名女生中任取2人“捆”在一起记作A,

A共有C32A22=6种不同排法,

剩下一名女生记作B,两名男生分别记作甲、乙;

则男生甲必须在A、B之间

此时共有6×2=12种排法(A左B右和A右B左)

最后再在排好的三个元素中选出四个位置插入乙,

∴共有12×4=48种不同排法.

故答案为:48.

单项选择题

Martin Luther King, Jr., is well known for his work in civil rights and for his many famous speeches, among them his moving "I Have A Dream" speech. But fewer people know much about King’s childhood. M. L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather, the Reverend A. D. Williams, purchased their home on Auburn Avenue in 1909, 20 years before M. L. was born. The Reverend Williams, an eloquent speaker, played an important role in the community since so many people’s lives centered around the church. He allowed his church and his home to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in this atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it.
M. L.’s childhood was not especially eventful. His father was a minister and his mother was a musician. He was the second of three children, and he attended all-black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was the main artery through a prosperous neighborhood that had come to symbolize achievement for Atlanta’s black people. It was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers and other black-owned or black-operated businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a seemingly insurmountable barrier that kept black Atlantans from mingling with whites.

The word,’ mingling" underlined in Paragraph 2 refers to ______.

A.interfering

B.gargling

C.consuming

D.associating

判断题