第四節　數量概念關系

考察能力及閱讀思維

GMAT閱讀考查考生對數量概念關系的理解能力，即要求考生對文中的數字信息進行分析，使用簡單的數學運算即可。

請看下面的例子：

例1：

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

請看下面的題目：

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時，tryptophan和serotonin下降。題目問增加protein時，起初作者認為會發生什么？由題目可知，題目問題和原文構成了對比關系，所以只需將原文中增加protein時，tryptophan和serotonin下降這個結果取非即可，即initially作者認為增加protein時，tryptophan和serotonin應該不下降。故，答案選（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.

請看下面的題目：

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數量關系，protein↑，t%/aa%↓，t--brain↓，即protein增加時t的濃度除以aa的濃度下降，t提供給大腦細胞的速度下降。故，答案選（A）。

閱讀思維

若一個段落出現有數量關系，務必讀懂數量之間的邏輯關系。由于數量關系經?？嫉氖钦撽P系、大于小于關系，因此盡可能地列出數量關系之間的變化。

以上是GMAT閱讀要求的閱讀能力和思維方式，希望各位考生在備考時多加練習和應用，從而更好地在考試中提高閱讀速度，提高讀文章時預測考點的能力以及定位的準確性。