请教一下关于数学思维的题目解答方法

qiqi_cola

30  A recent survey of all auto accident victims in Dole County found that,of the severely injured drivers and fron-seat passengers,80 percent 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 ot 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  Considerably more than 20 percent of drivers and front-seat passengers in Dole county always wear seat belts when traveling by car.

C  More drivers and front-seat 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  Most of the auto accidents reported to police in Dole County do not involve any serious injury.


Recent estimates predict that between 1982 and 1995 the greatest increase in the number of people 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 estimates above are accurate,which of the following conclusions can be drawn.

A  In 1982 more people were working in low-paying service occupations 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 Nonserivce occupations will account for the same share of total employment in 1997 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 occupations by 1995.

E  The rate of growth for low-paying service occupations will be greater than the overall rate of employment frowth between 1982 and 1995.


大家帮忙啊。

prince

这两道题都是一个涉及比例的题。不需要多少的数学知识。
1) 答案A.这道题是找假设。Not +weaken 是最好的方法。对A去反。假设少于20%的人were wearing seat belts at the time of their accidents。那么在作者的推理中有20%受伤的人是wearing seat belts。那么作者如何能得出 wearing seat belts更安全呢？（比如：总数的15%wearing seat belts，但有20%......）
2）答案A.记住比例大的增加同样的比例后，占总的比例要减少。本题可以举特殊的例子