新GRE数学考点：Combinations of Choices

　　今天针对新gre数学复习，小编给大家整理的是关于排列、组合的相关内容，这些概念在考试中一定会考到的。希望考生能再接再厉，取得一个好成绩，突破新gre数学难的困境。

　　Combinations of Choices

　　If there are n choices for one type and m choices for second type, then number of combinations for both types is the product of choices:nm.

　　Example:

　　If there are 3 kinds of breads to choose from and 4 kinds of meats, then we can make 34=12 different sandwiches.

　　If an alphabet has 26 letters, then the number of possible 2 letter word is 2626=676.All of them may not be vaild words.

　　Remember:

　　Do not add the choices to get the total combinations.

　　The product rule can be applied to more than two types of choices: if there are 3 kinds of breads, 4 kinds of meats, and 6 kinds of cheeses, then we can make 346=72 different sandwiches.

　　俗话说：工欲善其事必先利其器。有一部分考生认为新GRE数学具有一定的难度，这其中的原因是由于考生在复习时没有把新gre数学的基础打牢。想要新gre数学考好，复习的时候一定要把基本概念和重要考点都弄扎实。