春春_为你痴狂
幼苗
共回答了18个问题采纳率:94.4% 举报
第1种情况:后区中2个,前区中0个或1个
(1)后区中2个的概率:C(2,2)*C(0,10)/C(2,12)=1/66=0.015151515151515151515151515151515
前区中0个的概率:C(0,5)*C(5,30)/C(5,35)=142506/324632=0.43897705709849922373641538726928
前区中1个的概率:C(1,5)*C(4,30)/C(5,35)=5*27405/324632=0.42209332413317233051578402622046
(2)前区中0个或1个的概率,上面两值相加:0.861070381231671554252199413489
则第1种情况的概率:(1)*(2)=0.013046520927752599306851506264541
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第2种情况:后区中1个,前区中2个
(3)后区中1个的概率:C(1,2)*C(1,10)/C(2,12)=20/66=0.3030303030303030303030303030303
(4)前区中2个的概率:C(2,5)*C(3,30)/C(5,35)=10*4060/324632=0.12506468863205106089356563739865
则第2种情况的概率:(3)*(4)=0.037898390494560927543504738605417
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第3种情况:后区中0个,前区中3个
(5)后区中0个的概率:C(0,2)*C(2,10)/C(2,12)=45/66=0.68181818181818181818181818181818
(6)前区中3个的概率:C(3,5)*C(2,30)/C(5,35)=10*435/324632=0.013399788067719756524310604006999
则第3种情况的概率:(5)*(6)=0.0091362191370816521756663209131794
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总的概率,3种情况全部相加:
0.013046520927752599306851506264541+0.037898390494560927543504738605417+0.0091362191370816521756663209131794=0.060081130559395179026022565782 约等于1/16.6
1年前
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