GRE数学考点介绍：Conditional

　　Conditional

　　Probability of event A conditioned on the fact that event B has happened is called the conditional probability and written as P.

　　P=Probability Both A and B happens/ Probability B happens.

　　Example:

　　A six-sided die with faces from 1 to 6 is rolled twice. What is the probability that the face 5 turned up on first try given that the sum of the two faces is 9?

　　P=4/36=1/9.

　　P==1/36.

　　P==1/4

　　Remember:

　　If P=P,then two events A and B are independent, that is occurrence of one does not influence the other

　　以上就是GRE数学常考题总结，大家需要多加练习，总结易错点，进行集中突击。在考前，最好把错题都重看一遍，以免在考场上犯同样的错误。