老师，GRE数学的知识点挺简单，我都会。但有时候题目理解不准确，我理解的和题目表达的总会出现一点偏差，后面导致题做错，我该怎么办？我相信这不仅仅是个例，很多同学都会遇到数学表达看不懂的情况。今天我们就来讲几个大家经常犯糊涂的数学表达。
01
be divided by/be divisible by
常用形式为A is divided by B。在这句话中，同学经常搞不清楚是用谁除以谁。从字面翻译来看，“A被B除”应该A是被除数，B是除数，相当于A除以B。
同学们以后见到 be divided by，就把这个整体翻译成除号。
比如：
the number of prime numbers divisible by 13
翻译：除以13是整数的质数的个数
来个题目试一试：
Quantity A
the number of prime numbers divisible by 13
Quantity B
the number of prime numbers divisible by 2
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D. The relationship cannot be determined from the information given.
答案：C
解析：数量A：除以13是整数的质数的个数，只有1个，就是13自己。
数量B：除以2是整数的质数的个数，也只有1个，就是2自己。
A和B是数量的比较，都是1个，因此选C。
02
make up/be made up of
这两个短语都叫做“组成”，但是究竟谁组成谁同学又搞不清了。
A make up B
翻译：A组成B
其中B是一个整体，A相当于是B中的元素。
A is made up of B
翻译：A由B组成
其中A是整体，B是A中的元素。
来看这么一句话：
By weight, liquid A makes up 8 percent of solution R and 18 percent of solution S.
液体A组成R溶液的8%，液体A组成S溶液的18%。
换句话说，100g的溶液R里，有8%为液体A，即8克。同理，100g的溶液S中，有18%为液体A，即18克。
03 倍数表达
倍数表达也是令同学们头疼的一类表达，常常分不清到底谁是谁的几倍。
以下三种形式是倍数表达的常见形式：
There are A n times as many as B.
There are n times A as many as B.
There are n times as many A as B.

同学们会发现这里A的位置比较灵活。无论A放在哪儿，只要语序上在B的前面，表达的意思都是一样的，都是“A是B的n倍”，写成表达式为A=nB。
来看个句子试一试：
There are twice as many employees in Department X as in Department Y.
总结
今天讲了几个常见的数学表达，希望大家遇到以后不会再犯迷糊。
数学表达
中文理解
A is divided by B
A÷B
（A除以B）
A is divisible by B
A除以B是整数
A make up B
A组成B
A is made up of B
A由B组成
There are A n times as many as B.
There are n times A as many as B.
There are n times as many A as B.
A=nB
（A是B的n倍）