1.In a survey of 3630 college students,1162 stated that they cheated on an exam.If two students are randomly selected,find the probability that they both cheated on the exam.2.In a game of dice,a play receives $5 if the sum of dots on the dice is 4,$
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1.In a survey of 3630 college students,1162 stated that they cheated on an exam.If two students are randomly selected,find the probability that they both cheated on the exam.2.In a game of dice,a play receives $5 if the sum of dots on the dice is 4,$
1.In a survey of 3630 college students,1162 stated that they cheated on an exam.If two students are randomly selected,find the probability that they both cheated on the exam.
2.In a game of dice,a play receives $5 if the sum of dots on the dice is 4,$8 if the sum of the dots on the dice is 10.Otherwise the player loses $2.Find the expected value of the net gain of the palyer.
第一题是概率,第二题是期望.紧急!最好有解题过程.
1.In a survey of 3630 college students,1162 stated that they cheated on an exam.If two students are randomly selected,find the probability that they both cheated on the exam.2.In a game of dice,a play receives $5 if the sum of dots on the dice is 4,$
(1)
C(1162,2)/C(3630,2)= 0.1024
(2)
全部可能性有6x6=36种
总和是4的情况记顺序有‘(1,3),(3,1),(2,2)’
P(a)=3/36=1/12
总和是10的情况记顺序有(4,6)(6,4)(5,5)
P(b)=3/36=1/12
总和是其他点的概率为:1-(1/12+1/12)=5/6
期望E=5×1/12+8x1/12+(-2)x5/6=-7/12
有不解的可以问我 祝学习愉快
1.(1162/3630)*(1161 /3630)
2.骰子点数为4的概率为3/36,为10的概率为3/36
1/12*(-5)+1/12*(-8)+10/12*2=7/12$
楼上讲的很对,就是算反了