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[求助]
求解 已有2人參與
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一次考試共5道題,做對(duì)第1、2、3、4、5題的分別占參加人數(shù)的95%、80%、79%、74%、85%.如果做對(duì)三道或三道以上為合格,那么這次考試的合格率至少是多少?、 求各位給出解題過程,謝謝了。 |
專家顧問 (職業(yè)作家)
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專家經(jīng)驗(yàn): +831 |
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全錯(cuò)的: >> qc=0.05*0.2*0.21*0.26*0.15 qc = 8.1900e-005 對(duì)一道的: >> dy=0.95*0.2*0.21*0.26*0.15+0.05*0.8*0.21*0.26*0.15+0.05*0.2*0.79*0.26*0.15+0.05*0.2*0.21*0.74*0.15+0.05*0.2*0.21*0.26*0.85 dy = 0.0029 對(duì)兩道的: >> d2y1=0.95*0.8*0.21*0.26*0.15+0.95*0.2*0.79*0.26*0.15+0.95*0.2*0.21*0.74*0.15+0.95*0.2*0.21*0.26*0.85 d2y1 = 0.0253 >> d2y2=0.05*0.8*0.79*0.26*0.15+0.05*0.8*0.21*0.74*0.15+0.05*0.8*0.21*0.26*0.85 d2y2 = 0.0040 >> d2y3=0.05*0.2*0.79*0.74*0.15+0.05*0.2*0.79*0.26*0.85 d2y3 = 0.0026 >> d2y4=0.05*0.2*0.21*0.74*0.85 d2y4 = 0.0013 綜合及格率: >> 1-(qc+dy+d2y1+d2y2+d2y3+d2y4) ans = 0.9637 >> |

榮譽(yù)版主 (文壇精英)
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專家經(jīng)驗(yàn): +518 |
捐助貴賓 (正式寫手)
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這好像不是概率題,似是求最小交集的問題。無論對(duì)于做對(duì)了幾道題的情形(例如所有做對(duì)3道題的情況),都必有0.26的人做錯(cuò)第4道題,所以做對(duì)3題或3題以上至少有26%。我這么考慮問題對(duì)不對(duì)? 發(fā)自小木蟲Android客戶端 |
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