SAT官方每日一题 2017年5月10日.

SAT试题类型 Mathematics > Standard Multiple Choice Read the following SAT test question and then click on a button to select your answer. Of 5 employees, three are to be assigned an office and 2 are to be assigned a cubicle. If 3 of the employees are men and 2 are women, and if those assigned an office are to be chosen at random, what is the probability that the offices will be assigned to 2 of the men and 1 of the women? (A) 1 over 3 (B) 2 over 5 (C) 1 over 2 (D) 3 over 5 (E) 2 over 3 答案:D 解析: Explanation Of the 5 office workers, 3 are to be assigned an office. This is an example of combinations: to find the number of ways of choosing 3 of the 5 workers, you can count the number of ways of selecting the workers one at a time and then divide by the number of times each group of 3 workers will be repeated. There are 5 ways of choosing the first worker to get an office. Then there will be 4 ways of choosing the second worker to get an office, and 3 ways of choosing the third worker. This is a total of 5 times 4 times 3 = 60 possibilities. In these 60 possible selections, each distinct group of 3 workers will occur 3 times 2 times 1 = 6 times. (There are 3 possibilities for the first worker chosen from the group, 2 for the second worker chosen, and only 1 for the third.) Therore, there are 60 over 6 = 10 different ways the 3 workers who get an office can be chosen from the 5 workers. How many of these 10 possible groups of 3 workers consist of 2 men and 1 woman? From the 3 male workers, 2 can be chosen in 3 different ways. There are 2 possibilities for the female worker. Therore, 3 times 2 = 6 of the groups of 3 workers consist of 2 men and 1 woman. Since there are 10 different ways the 3 workers who get an office can be chosen, and 6 of these possible groups of 3 workers consist of 2 men and 1 woman, the probability that the offices will be assigned to 2 men and 1 woman is 6 over 10, or 3 over 5. 更多阅读 SAT官方每日一题 2011年5月3日 SAT官方每日一题 2011年5月4日 SAT官方每日一题 2011年5月5日 SAT官方每日一题 2011年5月6日 SAT官方每日一题 2011年5月7日 SAT官方每日一题 2011年5月8日 SAT官方每日一题 2011年5月9日