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[求助]Help me please!

Recent estimates predict that between 1982 and 1995 the greatest increase in the nember of people employed will be in the category of low-paying sevice occrpations. This category, however, will nor 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 workeng in low-paying service occupations than were working in high-paying wervice occupations.
B) In 1995 more people will be working in high-paying service occupations than will be workeng 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 in1982 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 growth between 1982 and 1995.[em05][em05]
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[em08]

[此贴子已经被作者于2003-4-1 22:24:27编辑过]

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I THINK IS A,
JUST TRANSFER IT TO A MATHEMTICA PROBLEM, AND YOU WILL GET THE ANSWER.
I came, I suffered, I survived.

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isuffering正确!

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不是很明白,

能具体写一下怎么算嘛?

谢谢

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To Odyuibe:

Just teach fish to swim!

将这题转化成数学推导应该是比较直观一些:

设几个参数:
(1) 1982年低收入职业的人数为A1, 高收入职业人数为A2
(2) 1982年至1995年
      低收入职业增加人数为a1, 高收入职业增加人数为a2

由题意得出三条式子:
(1)the greatest increase in the number of people employed will be in the
        category of low-paying service occupations
        ==》a1>a2

(2)this category, however, will not increase its share of total employment
        ==》A1/(A1+A2) >= (A1+a1)/(A1+a1+A2+a2)

(3)whereas the category of high-paying service occupations will increase its share
        ==》A2/(A1+A2) < (A2+a2)/(A1+a1+A2+a2)

为简化(2),(3)两个式子,设
1/(A1+A2) = K   
1/(A1+a1+A2+a2) = P
(这里我要打一个伏笔:K>

则(2)(3)两个式简化为
A1*K >= (A1+a1) * P  即  (K-P)* A1 >= P * a1  (4)
A2*K <  (A2+a2) * P   即  (K-P)* A2 < P * a2  (5)

由于 a1>a2,我们很快得出 P * a1 > P * a2

因此,从(4)(5)两个式子中,即可得出
(K-P)* A1  >=  P * a1  > P * a2  > (K-P)* A2

简化得出:(K-P)* A1 > (K-P)* A2  
刚才在上面我已证明了K>, 所以K-P>0

最后得出答案A的结论: A1 > A2
(in 1982 more people were workeng in low-paying service occupations than
were working in high-paying wervice occupations.)

其实这道题的推导并不算严密,因为只考虑了只有高收入和低收入存在的情况,但是即使考虑其它因素,例如可能有中收入存在的情况。 那们也只需再设多一个参数,按上述步骤,一样可推出A的结论, 在此就不再赘述了。

别看上述推导那么复杂,其实在草稿纸上划几下就出来了。


[此贴子已经被作者于2003-4-10 12:01:36编辑过]

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