题目

在一个不透明的袋子中装有 4 个红球和 6 个黄球，这些球除颜色外都相同，将袋子中的球充 分摇匀后，随机摸出一球. （1）分别求摸出红球和摸出黄球的概率 （2）为了使摸出两种球的概率相同，再放进去 8 个同样的红球或黄球，那么这 8 个球中红球和 黄球的数量分别是多少？ 答案：【答案】（1）P（摸到红球）＝，P（摸到黄球）＝；（2）5 个， 3 个. 【解析】（1）直接利用概率公式计算即可求出摸出的球是红球和黄球的概率；（2）设放入红球x个，则黄球为（8−x）个，由摸出两种球的概率相同建立方程，解方程即可求出8个球中红球和黄球的数量分别是多少．（1）∵袋子中装有44、People can be addicted to different things – e, g alcohol, drug, certain foods, or even television. People who have such an addiction are compulsive （强迫的）; they have a very powerful psychological need that they feel they must satisfy. According to psychologists, many people are compulsive spenders. They feel that they must spend money. This compulsion, like others, is impossible to explain reasonably. For compulsive spenders who buy on credit, charge accounts are even more exciting than money. In other words, compulsive spenders feel that with credit, they can do anything. Their pleasure in spending large amounts is actually greater than the pleasure that they get from the things they buy. 　　There is even a special psychology of bargain hunting. To save money, of course, most people look for sales, low prices, and discounts. Compulsive bargain hunters, however, often buy things that they don’t need just because they are cheap. They want to believe that they are helping their budgets, but they are really playing an exciting game. When they can buy something for less than other people, they feel that they are winning. Most people, experts claim, have two reasons for their behavior: a good reason for the things that they do and the real reason. 　　It is not only scientists, of course, who understand the psychology of spending habits, but also business people. Stores, companies, and advertisers use psychology to increase business. They consider people’s needs for love, power, or influence, their basic values, their beliefs and opinions, and so on in their advertising and sales methods. 　　Psychologists often use a method called behavior therapy（疗法） to help individuals solve their personality problems. In the same way, they can help people who feel that they have problems with money. 1．According to the psychologists, a compulsive spender is one who spends large amounts of money __    ___. 　　A．and takes great pleasure from what he or she buys 　　B．in order to satisfy his or her basic needs in life 　　C．and feels he or she is cheated 　　D．just to meet his or her strong psychological need 2．Which of the following statements is TRUE according to the text? 　　A．People spend money for exactly the same reason that they need to buy things. 　　B．Business people understand the psychology of compulsive buying better than scientists do. 　　C．Compulsive bargain hunters do not have problems with money. 　　D．Business people and advertisers can use the psychology of peoples’ habits to merest sales. 3．What is the text mainly about? 　　A．The habits of compulsive spenders. 　　B．The psychology of money-spending habits. 　　C．A special psychology of bargain hunting. 　　D．The use of the psychology of spending habits in business. 4．From the text we may safely conclude that compulsive spenders or compulsive bargain hunters ___   __. 　　A．are really reasonable 　　B．are really beyond drugs 　　C．need special treatment 　　D．can never get any help to solve their problems with money