问几道数学相关类的归纳题/CXD-30,33,48

陈向东逻辑推理上的题目,都是和数字比例有关的一类题,不是太明白:

假设题:

30.Although the ratio of physicians to total population is about  the same in the United States and Canada,the United states has 33 percent more surgeons per capita.clearly, this is the reason people in the united states undergo 40 percent more operations p[er capita than do Canadians.

the explaination given above rests  on an assumption that

a)patients in the united states do not have a greater need for surgery than do patients in Canada

b)the population of the Unites states is not larger than that of Canada

c)united State patients sometimes travel to Canada for certain kinds of surgery

d)general practitioners in the united states do not as a rule examine a patient who is a candidate for surgery before sending the patient to a surgeon

e) there are not unneccessary surgical operations performed in Canada

答案为A 我选的D

归纳题:

48.Figures issued by the government of a certain country show that in 1980 the public sector and the private sector each employed the same number of people.between 1980 and 1984,according to the government,total employment decreased in the public sector more than it increased in the private sector.

if,according to governmental figures,the unemployment rate in this country was the same in both 1980 and 1984,which of the following statements must be true about this country?

a) fewer people were in the labor force,as counted by the government,in 1984 than in 1980

b)the competition for the available work increased between 1980 an d1984

c)the government's figures for total employment increased between 1980 and 1984

d)the number of people counted by the government as unemployed was the same in 1980 and 1984

e)in 1984 more people sought work in the private sector than in the public sector

答案为A 但觉得正好是反的1984的labor force应该更多?

30. A recent survey of all auto accident victims in Dole county found that,of the severely injured drivers and front passengers,80% were not wearing seat belts at the time of their accidents.this indicates that,by wearing seat belts,drivers and front-seat passengers can greatly reduce their risk of being severely injured if they are in an auto accident.

the conclusion above is not properly drawn unless which of the follwing is true?

a)of all the drivers and front passengers in the survey,more than 20% were wearing seat belts at the time of their accident

b)considerably more than 20% of drivers and front passengers in Dole county always wear seat belts when  travelling by car

c)more drivers and front passengers in the survey than rear-seat passengers were very severely injured

d)more than half of the drivers and front-seat passengers in the survey were not wearing seat belts at the time of their accidents

e)more of the auto accidents reported to police in Dole county do not invlove any serious injury

答案为A 不明白怎么得出的

33.recent estimates predict that between 1982 and 1995 the greatest  increase in the number of people employed will be in the category of low-paying service occupations.this category,however,will not increase  its share of total employment.whereas the category of high-paying service occupations will increase its share.

if the estimate above are accurate,which of the follwing conclusions can be drawn?

a)in 1982 more people were working in low-paying service occcupations than were working in high-paying service occupations

b)in 1995 more people will be working in high-paying service occupations than will be working  in low-paying service occupations

c)nonservice occupations will account for the same share of total employment in 1995 as in 1982

d)many of the people who were working in low-paying service occupations in 1982 will be working in high-paying service ocupations by 1995

e)the rate of growth for low-paying service occupations will be greater than the overall rate of employment grownth between 1982 and 1995

答案为A  不明白

特别摸不着方向 可能是一些基本规律没有掌握 这类题的解题思路大概是怎样的呢?需要算一算吗?

请NN指点!