GRE数学考点：At Least Once

　　新GRE数学考试的考点都是高中时候学到的知识点，考生不要过于紧张，把基本概念弄明白，再记住一些新GRE数学必备的词汇，那么相信新GRE数学应该没有问题。下面GRE（gre.xdf.cn）给大家整理的是关于At Least Once的相关内容，希望对各位考生有所帮助。

　　At Least Once

　　If probability of an event happening is p, then the probability that the event happens at least once in n trials is 1-n.

　　Example:

　　To understand the equation follow these steps:

　　1.The probability of the event not happening is 1-p.

　　2.The probability it wont happen n-times in a row is n.

　　3.Probability it will happen at least once is 1-n.

　　Probability that a roll of a six-sided die land with face 1 is 1/6.Then the probability that 1 will turn up at least once in 3 tries:=1-3=1-3.

　　Remember:

　　It is much harder to directly calculate the at-least-once probability.

　　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。祝大家都能取得理想成绩!