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又是概率问题~Atwo-sidedcoinisflippedfourtimes.Giventhatthecoinlandedheadsupmorethantwice,whatistheprobabilitythatitlandedheadsupallfourtimes?我用的是TI-84Plus的计算器最好能用nPr和nCr的符号讲解万

题目详情
又是概率问题~
A two-sided coin is flipped four times. Given that the coin landed heads up more than twice, what is the probability that it landed heads up all four times?
我用的是TI-84 Plus的计算器
最好能用nPr和nCr的符号讲解
万分感谢~
▼优质解答
答案和解析
已知向上超过2次,3次的有C(3,4)=4种,4次的有C(4,4)=1种
所以共有1+4=5种情况,4次向上只有一种情况,几率为1/5