WBJEE · Maths · Probability
In order to get a head at least once with probability \(\geq 0.9\), the minimum number of times a unbiased coin needs to be tossed is
- A 3
- B 4
- C 5
- D 6
Answer & Solution
Correct Answer
(B) 4
Step-by-step Solution
Detailed explanation
We have, \(P(H)=\frac{1}{2}, P(T)=\frac{1}{2}\) Now, \(P(X \geq 1)=1-P(X=0\) \(=1-{ }^{n} C_{o}(p)^{0}(q)^{n}=1-\left(\frac{1}{2}\right)^{n}\) \(1-\frac{1}{2^{n}} \geq 0.9\) \(\Rightarrow\) \(0.1 \geq \frac{1}{2 n}\) \(\Rightarrow\) \(\frac{1}{10} \geq \frac{1}{2^{n}}\)…
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