旧PREP1-23 玻璃瓶问题（再讨论）

lilian0807

23.(29107-!-item-!-188;#058&003854)

From 1978 to 1988, beverage containers accounted for a steadily decreasing percentage of the total weight of household garbage in the United States.  
The increasingly widespread practice of recycling aluminum and glass was responsible for most of this decline.  
However, although aluminum recycling was more widely practiced in this period than glass recycling, it was found that the weight of glass bottles in household garbage declined by a greater percentage than the weight of aluminum cans.

Which of the following, if true of the United States in the period 1978 to 1988, most helps to account for the finding?

(A) Glass bottles are significantly heavier than aluminum cans of comparable size.

(B) Recycled aluminum cans were almost all beverage containers, but a significant fraction of the recycled glass bottles had contained products other than beverages.

(C) Manufacturers replaced many glass bottles, but few aluminum cans, with plastic containers.

(D) The total weight of glass bottles purchased by households increased at a slightly faster rate than the total weight of aluminum cans.

(E) In many areas, glass bottles had to be sorted by color of the glass before being recycled, whereas aluminum cans required no sorting.

这道题目纠结了很久，翻了论坛上的帖子还是没搞明白，后来看了Ron的解释，觉得似乎有点头绪了，写出来供讨论。
先贴上Ron的原话
this problem turns on the differences between PERCENTAGES and ABSOLUTE NUMBERS.
facts:
* the PERCENTAGE of recycled aluminum was higher than the PERCENTAGE of recycled glass. this is what it means when we say that aluminum recycling was more widely practiced.
BUT
* the NUMERICAL CHANGE in aluminum in the trash was lower than the NUMERICAL CHANGE in glass in the trash.

if all the stuff missing from the trash had been recycled, this would be impossible. therefore, we need another explanation, besides recycling, for WHY THE TOTAL USE OF GLASS HAS GONE DOWN. that's the only way that these findings are mathematically possible.
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我的理解是这样的：
although aluminum recycling was more widely practiced in this period than glass recycling

这句话是说铝的回收比例>玻璃的回收比例

the weight of glass bottles in household garbage declined by a greater percentage than
the weight of aluminum cans

我觉得这句话中in household garbage是个修饰成分，也就是说weight of glass（和其自身比）的下降比例
大于weight of aluminum的下降比例，也就是说WG2-WG1/WG1要大于WA2-WA1/WA1
等同于玻璃的回收比例>铝的回收比例，所以和前面的条件矛盾
因此是它因导致玻璃瓶减少

不知道我的想法对不对，欢迎大家拍砖

although aluminum recycling was more widely practiced in this period than glass recycling

这句话是说铝的回收比例>玻璃的回收比例

the weight of glass bottles in household garbage declined by a greater percentage than
the weight of aluminum cans

我觉得这句话中in household garbage是个修饰成分，也就是说weight of glass（和其自身比）的下降比例
大于weight of aluminum的下降比例，也就是说WG2-WG1/WG1要大于WA2-WA1/WA1
等同于玻璃的回收比例>铝的回收比例，所以和前面的条件矛盾
因此是它因导致玻璃瓶减少

不知道我的想法对不对，欢迎大家拍砖

HarrisZheng

你都自问自答了