问题 解答题

有10双互不相同的鞋子混装在一只口袋中,从中任意取出4只,试求出现以下结果时各有多少种情况?

(1)4只鞋子恰成两双;

(2)4只鞋子没有成双的.

答案

(1)45;(2)3360.

第一问中利用古典概型概率公式可知,只需选出两双鞋,所以有=45(种)情况.

第二问中,利用4只鞋若没有成双的,则它们来自于4双鞋;先从10双中取4双,有C种取法,再从每双中取一只,各有C种取法,所以由分步乘法计数原理共有

·=3 360(种)情况

解: (1)根据题意只需选出两双鞋,所以有=45(种)情况.

(2)方法一:4只鞋若没有成双的,则它们来自于4双鞋;先从10双中取4双,有C种取法,再从每双中取一只,各有C种取法,所以由分步乘法计数原理共有

·=3 360(种)情况.

阅读理解

Researchers are placing robotic dogs(机器狗)in the homes of lonely old people to determine whether they can improve the quality of life for humans. Alan Beck, an expert in human-animal relationship, and Nancy Edwards, a professor of nursing, are leading the animal-assisted study concerning the influence of robotic dogs on old people’s depression, physical activity, and life satisfaction. “No one will argue that an older person is better off being more active, challenged, or stimulated(应急的) ,”Edwards points out. “The problem is how we promote that, especially for those without friends or help. A robotic dog could be a solution.”

In the study, the robot, called AIBO, is placed for six weeks in the houses of some old people who live alone. Before placing AIBO in the home, researchers will collect baseline data for six weeks. These old people will keep a diary to note their feelings and activity before and after AIBO. Then, the researchers will review the data to determine if it has inspired any changes in the life of its owner.

“I talk to him all the time, and he responds to my voice,” says a seventy-year-old lady, “When I’m watching TV, he’ll stay in my arms until he wants down. He has a mind of his own.”

The AIBOs respond to certain orders. The researchers say they have some advantages over live dogs, especially for old people. Often the elderly are disabled(行动不便的) and cannot care for an animal by walking it or playing with it. A robotic dog removes(免除) exercise and feeding concerns.

“At the beginning, it was believed that no one would relate to the robotic dog, because it was metal and not furry.” Beck says,“But it’s amazing how quickly we have given up that belief.”

“Hopefully, down the road, these robotic pets could become a more-valuable health helper. They will record their masters’ blood pressure, oxygen levels, or heart rhythms. AIBOs may even one day have games that can help stimulate older people’s minds.”

小题1: The purpose of Beck and Edwards’ study is to        .

A.understand human-animal relationship

B.find the causes of old people’s loneliness

C.make lonely old people’s life better

D.promote the animal-assisted research小题2:In the research, the old people are asked to        .

A.note the activities of AIBOs

B.record their feelings and activity

C.keep AIBOs at home for 12 weeks

D.analyze the collected information小题3:What is the advantage of AIBO over live dogs?

A.It is easier to keep at home.

B.It responds to all the human orders.

C.It can help the disabled people.

D.It can watch TV with its owner.

单项选择题