新版GRE数学复习重要考点:At Least Once

所属专题:GRE数学重要考点  来源:互联网    要点:GRE考试  
编辑点评: 新GRE数学考试的难度有所增加,但是只要大家认真准备,掌握了基本的知识,还是可以在原有的水平上考出出色的分数的。本文为大家整理汇总了新GRE数学考试的复习要点,希望对大家的复习有所帮助。

新版GRE数学复习重要考点: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.

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