Respuesta :
Answer:
(a) P = 0.0001
(b) P = 0.6561
(c) P = 0.2916
(d) P = 0.3439
(e) P = 0.2
Step-by-step explanation:
This is a probability problem.
The dice is rolled 4 times (n=4) and we calculate the probability of different outcomes.
The probability of a 6 in a roll is 0.5.
The probability of a 1, 2, 3, 4 or 5 in a roll is 0.5/5=0.1.
a) Outcome: all the rolls are 2.
The probability of having a 2 in a roll is 0.1, so we can calculate the probability of having a 2 in four consecutive rolls as
[tex]P(x1=2;x2=2;x3=2;x4=2)=P(x=2)^4=0.1^4=0.0001[/tex]
b) Outcome: none of the rolls is a 2.
The probability of having any other number but 2 in 4 rolls is:
[tex]P(x1\neq2;x2\neq2;x3\neq2;x4\neq2)=P(x\neq2)^4=(1-0.1)^4=0.6561[/tex]
c) Outcome: exactly one roll is a 2
This is the sum of the probability of having a 2 in the first, second, third or fouth roll, and others numbers in the rest of the rolls. These 4 combinations have the same probability, so we will multiply it by 4.
[tex]P(exactly \,one\,2)=4*P(x1=2;x2\neq2;x3\neq2;x4\neq2)\\\\P(exactly \,one\,2)=4*0.1*0.9*0.9*0.9=0.2916[/tex]
d) Outcome: at least one of the rolls is a 2
In this case, is the probability of having at least one 2, is the sum of the probability of getting a 2 in the first roll, the probability of getting a 2 in the second roll, the probability of getting a 2 in the third roll and the probability of getting a 2 in the four roll:
[tex]P(x1=2)+P(x2=2)+P(x3=2)+P(x4=2)=0.1+0.9*0.1+0.9*0.9*0.1+0.9*0.9*0.9*0.1\\\\P(x1=2)+P(x2=2)+P(x3=2)+P(x4=2)=0.1+0.09+0.081+0.0729\\\\P(x1=2)+P(x2=2)+P(x3=2)+P(x4=2)=0.3439[/tex]
e) Outcome: either the first roll or the last roll is a 2
The probability of getting a 2 in the first roll is equal to having it in a fourth roll, and its the probability of getting a 2 in a roll (multiplied by 2, beacuse there can be either in the first or in the last roll).
[tex]P(x1=2)+P(x4=2)=2*P(x=2)=2*0.1=0.2[/tex]
