第四节　数量概念关系

考察能力及阅读思维

GMAT阅读考查考生对数量概念关系的理解能力，即要求考生对文中的数字信息进行分析，使用简单的数学运算即可。

请看下面的例子：

例1：

Surprisingly, however, when we added a large amount of protein to the meal, brain tryptophan and serotonin levels fell.

请看下面的题目：

It can be inferred from the passage that the authors initially held which of the following hypotheses about what would happen when they fed large amounts of protein to rats?

（A） The rats' brain serotonin levels would not decrease

（B） The rats' brain tryptophan levels would decrease

（C） The rats' tyrosine levels would increase less quickly than would their leucine levels

（D） The rats would produce more insulin

（E） The rats would produce neurotransmitters other than serotonin

【解析】由原文可知，增加protein时，tryptophan和serotonin下降。题目问增加protein时，起初作者认为会发生什么？由题目可知，题目问题和原文构成了对比关系，所以只需将原文中增加protein时，tryptophan和serotonin下降这个结果取非即可，即initially作者认为增加protein时，tryptophan和serotonin应该不下降。故，答案选（A）。

例2：

The more protein in the meal, the lower is the ratio of the resulting blood-tryptophan concentration to the concentration of competing amino acids, and the more slowly is tryptophan provided to the brain. Thus the more protein in a meal, the less serotonin subsequently produced and released.

请看下面的题目：

According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with the

（A） amount of protein present in a meal

（B） concentration of serotonin in the brain before a meal

（C） concentration of leucine in the blood rather than on the concentration of tyrosine in the blood after a meal

（D） concentration of tryptophan in the brain before a meal

（E） number of serotonin-containing neurons present in the brain before a meal

【解析】由原文可以得到如下的数量关系，protein↑，t%/aa%↓，t--brain↓，即protein增加时t的浓度除以aa的浓度下降，t提供给大脑细胞的速度下降。故，答案选（A）。

阅读思维

若一个段落出现有数量关系，务必读懂数量之间的逻辑关系。由于数量关系经常考的是正负关系、大于小于关系，因此尽可能地列出数量关系之间的变化。

以上是GMAT阅读要求的阅读能力和思维方式，希望各位考生在备考时多加练习和应用，从而更好地在考试中提高阅读速度，提高读文章时预测考点的能力以及定位的准确性。