Let there be three independent events $E_1$, $E_2$ and $E_3$. The probability that only $E_1$ occurs is…

Let there be three independent events $E_1$, $E_2$ and $E_3$. The probability that only $E_1$ occurs is $\alpha$, only $E_2$ occurs is $\beta$ and only $E_3$ occurs is $\gamma$. Let $p'$ denote the probability of none of events occurs that satisfies the equations $(\alpha-2\beta)p=\alpha\beta$ and $(\beta-3\gamma)p=2\beta\gamma$. All the given probabilities are assumed to lie in the interval $[0,1]$. Then, the $\frac{\text{Probability of occurrence of } E_1}{\text{Probability of occurrence of } E_3}$ is equal to ________.

Solution

Let PE1=P1;PE2=P2;PE3=P3

PE1E¯2E¯3=α=P11-P21-P3 1

PE¯1E2E¯3=β=1-P1P21-P3 2

PE¯1E¯2E3=γ=1-P11-P2P3 3

PE¯1E¯2E¯3=p=1-P11-P21-P3 4

Given that, (α-2β)p=αβ

P11-P21-P3-21-P1P21-P3p=P1P2

1-P11-P21-P32

P11-P2-21-P1P2=P1P2

P1-P1P2-2P2+2P1P2=P1P2

P1=2P2 1

and similarly, (β-3γ)P=2βγ

P2=3P3 2

So, P1=6P3P1P3=6

Asked in: JEE Main 2021 (17 Mar Shift 1)

Practice more Probability questions on Aicharya