问题 解答题

甲、乙、丙、丁四位同学进行一次乒乓球单打比赛,要从中选出两位同学打第一场比赛.    

(1)请用树状图法或列表法,求恰好选中甲、乙两位同学的概率;

(2)若已确定甲打第一场. 再从其余三位同学中随机选取一位,求恰好选中乙同学的概率。

答案

解:(1)列表法如下:

所有可能出现的情况有 12 种.其中甲乙两位同学组合的情况有两种, 所以 P(甲乙)=

(2)若已确定甲打一场,再从其余三位同学中随机选取一位,共有3 种情况,选中乙的情况有一种

所以 P(恰好选中乙同学)=

单项选择题
阅读理解

WHEN there are some strangers in front of us, which of them will we trust?

According to a new study in the online PLOS One, people make their decisions to trust others largely based on their faces. Your appearance can do a lot for you, especially if you are in the financial industry. The more trustworthy you look, the more likely people will buy what you’re selling.

Researchers from Britain’s University of Warwick Business School, University College London, and Dartmouth College, US, did a number of experiments.

The research team used computer software to make 40 faces, from the least to the most trustworthy-looking.

The study said that the difference between a trustworthy face and one that isn’t as trustworthy comes from features that look slightly angry or slightly happy, even when the face is at rest. However, a slightly happy face is more likely to be trusted.

Researchers gave participants some money and asked them which face they trusted to invest the money for them. Then researchers gave some good and bad information about the people with these faces, and asked the participants again whom they trusted.

The results showed that even if they got different information, the participants didn’t change their choices. They were still more likely to invest their money with the more trustworthy-looking faces.

Chris Olivola, one of the study’s authors, said in the University of Warwick’s press release: “It seems we are still willing to go with our own instincts (本能) about whether we think someone looks like we can trust them. The temptation (诱惑) to judge strangers by their faces is hard to resist.”

小题1:Which of the following can be a proper title for this passage?

A.What kind of face do you trust?

B.Who did the experiments?

C.Why do you trust him or her?

D.Why did they do the experiments?小题2:According to the study, which of the following faces is most likely to be trusted?

A.A sad face.

B.A smiling face.

C.A crying face.

D.An angry face.小题3:Which of the following about the experiment is TRUE?

A.The trustworthy faces were given good information.

B.Researchers took photos of the 40 people’s faces in college.

C.Most participants gave their money to the trustworthy-looking faces.

D.Participants liked to choose the faces with good information.小题4:What did the researchers learn from their experiment?

A.People can’t refuse temptations.

B.People always do things with their instincts.

C.People often judge strangers by their faces.

D.People don’t trust strangers with sad faces.