这句话的正确理解是………

lala

the cost of producing electric power at photovoltaic plants was less than 20 times the cost of producing power at traditional plants. 摘自LSAT

光电设备制造电能的成本小于传统设备发电的20倍 or
光电设备制造电能的成本是  传统设备发电的1/20
请问，以上理解哪个正确？

tongxun

对不起，到现在才回答。虽凌晨2点晚了点，但刚才停电上不了网！
答案：下面

lala

别说对不起，非常感谢。只是奇怪，你干嘛这么晚不睡？

tongxun

lala：我白天的工作特别多，晚上必须挤出更多的时间看书。说真的，现在每天都一脸憔悴。但能看到大家到我们论坛来，我很开心，因为有许多的G友到坛中来只是匆匆而过，每当看到这种场面我都觉得很伤心，众人拾柴火焰高，还希望你能常来。若你觉得我们的论坛有什么不足之处，还请指正！到版务中发贴。我们会每天检查的。

liziyao

the cost of producing electric power at photovoltaic plants was less than 20 times the cost of producing power at traditional plants. 摘自LSAT

光电设备制造电能的成本小于传统设备发电的20倍 or  
我认为这句话的解释是对的。

tongxun

我写错了。是上面！光电设备制造电能的成本小于传统设备发电的20倍

lala

我更糊涂了。如果正确理解是下面一句，那么就好理解。若是上面的一句，那么题就有问题。请看原题。
12. Photovoltaic power plants produce electricity from sunlight. As a result of astonishing recent technological advances, the cost of producing electric power at photovoltaic power plants, allowing for both construction and operating costs, is one-tenth of what it was 20 years ago, whereas the corresponding cost for traditional plants, which burn fossil fuels, has increased. Thus, photovoltaic power plants offer a less expensive approach to meeting demand for electricity than do traditional power plants.
The conclusion of the argument is properly drawn if which one of the following is assumed?
(A) The cost of producing electric power at traditional plants has increased over the past 20 years.
(B) Twenty years ago, traditional power plants were producing 10 times more electric power than were photovoltaic plants.
(C) None of the recent technological advances in producing electric power at photovoltaic plants can be applied to producing power at traditional plants.
(D) Twenty years ago, the cost of producing electric power at photovoltaic plants was less than 20 times the cost of producing power at traditional plants.
(E) The cost of producing electric power at photovoltaic plants is expected to decrease further, while the cost of producing power at traditional plants is not expected to decrease.

该题选D。我觉得D也不对，没正确选项。题中说：太阳能发电的成本是20年前的1/10, 传统发电成本提高了，因此太阳能发电比传统发电更经济。问下面哪项假设使上面论断合理推出。答案如果是：20年前，太阳能发电成本比小于传统发电的20倍，我对20倍就有疑问，应该是10倍才对，你们觉得呢??

tongxun

lala：收到我发给你的短信了？现在与你讨论这题：
设原光电为X，则现在为X*1/20，
设原火电为Y，现在为YY，则YY》Y（has increased.）。由于X《20*Y，故X*1/20〈Y，对吧。因此，X*1/20〈YY。所以，结论（photovoltaic power plants offer a less expensive approach ）成立！