Minimum number of times a fair coin must be tossed

Question:

Minimum number of times a fair coin must be tossed so that the probability of getting at least one head is more than $99 \%$ is :

  1. 5

  2. 6

  3. 7

  4. 8


Correct Option: , 3

Solution:

$1-\left(\frac{1}{2}\right)^{n}>\frac{99}{100}$

$\Rightarrow\left(\frac{1}{2}\right)^{\mathrm{n}}<\frac{1}{100}$

$\Rightarrow \mathrm{n}=7$

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