[求助]逻辑难题中的数学

各位大侠，这三道题我都不会，是同类型的全部选A，哪位能和我讲讲这类题应该怎么做吗，我一看到就犯晕。万分感谢！！

一、a ten year comparison between the Unite State and the Soviet Union in term of crop yields per acre revealed that when only planted acreage is compared,Soviet yields are equal to 68 percent of Unite State yields, When total agricultural acreage (planted acrage plus fallow acreage) is compared, however, Soviet,yield is 114 percent of Unite States yield.                                             

From the information above, which of the following can be most reliably inferred about United States and Soviet agricultrue during the ten year period?                                                             

A

a higher percentage of total agricutural acreage was fallow in the Unite States than in the Soviet Union.                                                                  

B

Few total acres of available agricutural land were fallow in the Soviet Union than in the United States.                            

C

the Soviet union had more plant acreage than fallow acreage.

二、a recent survey of all auto accident victims in Dole County found that, of the severly injured drivers and front seat pasengers, 80 percent were not wear 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 serverely injured if they are in an auto accident.                                             

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

   A

Of all the drivers and front seat passengers in the survey, more than 20 percent were wearing seat belts at the time of their accidents.                                    

 B

More than half of the drivers and front seat passenger in the survey were not wear seat belts at the time of their accident.

三、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 occuptions. This category, however, will not increase its share of total employment , whereaes the category of high-paying service occuptions.     

  if the estimates above are accurate, which of the following conslusion can be drawn?
    

A

in 1982 more people were working in high-paying service occupations.                           

 B

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

作这类题最好拿笔在纸上划一划,主要是文章里的数字关系弄明白. 怎样弄明白:就是你要把文章看懂了.一边看一边划.

要注意那些数字是怎么蹦出来的. 然后再去看选项. 一般来说CR里的数字题不会考很难的数学推理.