求PREP-DS-1-201 思路

201.
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Martha bought an armchair and a coffee table at an auction and sold both items at her store.  Her gross profit from the purchase and sale of the armchair was what percent greater than her gross profit from the purchase and sale of the coffee table?

(1)  Martha paid 10 percent more for the armchair than for the coffee table.

(2)  Martha sold the armchair for 20 percent more than she sold the coffee table.

答案: E

看了就晕了,请高人指点

我的理解，问题是求 armchair的gross profit比coffee table的gross profic大多少个百分点:  gross profit=Sales price - Purchase price

可得，[(Sa - Pa) - (Sct - Pct)] / (Sct - Pct)          

（1）、（2）单独显然求不出解来

设Pct=x, Sct=y   (1)可得到 Pa=1.1x , (2)可得 Sa=1.2y  

结合（1）、（2）得： [(1.2y - 1.1x) - (y - x)] / (y - x) = (1.2y - 1.1x)/(y - x) - 1      同样没有结果，所以选E

以上仅代表个人观点，有不足的请NN指正.