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。下面新东方网GRE频道(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-(1-p)∧n.
Example:
To understand the equation follow these steps:
1.The probability of the event not happening is 1-p.
2.The probability it won't happen n-times in a row is (1-p)∧n.
3.Probability it will happen at least once is 1-(1-p)∧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-(1-1/6)∧3=1-(5/6)∧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!