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Question: Answered & Verified by Expert
In a binomial distribution $B\left(n, p=\frac{1}{4}\right)$, if the probability of at least one success is greater than or equal to $\frac{9}{10}$, then $n$ is greater than
MathematicsProbabilityJEE MainJEE Main 2009
Options:
  • A
    $\frac{1}{\log _{10}{ }^4-\log _{10}{ }^3}$
  • B
    $\frac{1}{\log _{10} 4+\log _{10} 3}$
  • C
    $\frac{9}{\log _{10}{ }^4-\log _{10} 3}$
  • D
    $\frac{4}{\log _{10}{ }^4-\log _{10} 3}$
Solution:
2731 Upvotes Verified Answer
The correct answer is:
$\frac{1}{\log _{10}{ }^4-\log _{10}{ }^3}$
$$
1-q^n \geq \frac{9}{10} \Rightarrow\left(\frac{3}{4}\right)^n \leq \frac{1}{10} \Rightarrow n \geq-\log _{\frac{3}{4}} 10 \Rightarrow n \geq \frac{1}{\log _{10}{ }^4-\log _{10}{ }^3}
$$

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