Probability 3 Question 45

45. Of the three independent events E1,E2 and E3, the probability that only E1 occurs is α, only E2 occurs is β and only E3 occurs is γ. Let the probability p that none of events E1,E2 or E3 occurs satisfy the equations

(α2β),p=αβ and (β3γ)p=2βγ. All the given probabilities are assumed to lie in the interval (0,1).

Then,  probability of occurrence of E1 probability of occurrence of E3 is equal to

Passage Type Questions

Passage

Football teams T1 and T2 have to play two games against each other. It is assumed that the outcomes of the two games are independent. The probabilities of T1 winning, drawing and losing a game against T2 are 12,16 and 13, respectively. Each team gets 3 points for a win, 1 point for a draw and 0 point for a loss in a game. Let X and Y denote the total points scored by teams T1 and T2, respectively, after two games.

(2016 Adv.)

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Answer:

Correct Answer: 45. (c)

Solution:

  1. PLAN

Forthe events to be independent,

P(E1E2E3)=P(E1)P(E2)P(E3)P(E1E¯2E¯3)=P( only E1 occurs )=P(E1)(1P(E2))(1P(E3))

Let x,y and z be probabilities of E1,E2 and E3, respectively.

α=x(1y)(1z)β=(1x)y(1z)γ=(1x)(1y)zp=(1x)(1y)(1z)

Given, (α2β)p=αβ and (β3γ)p=2βγ

From above equations, x=2y and y=3z

x=6zxz=6



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