=0.75*0.25*0.25+0.25*0.75*0.25+0.25*0.25*0.75

来源: (乐哈哈) 于 2010-01-11 20:09:22 [] [旧帖] [给我悄悄话] 阅读数 : (54 bytes)

=0.75*0.25*0.25+0.25*0.75*0.25+0.25*0.25*0.75
=9/64

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