The minimum number of times one has to toss a fair coin so that the probability of observation at least one head is at least 90% is :

  • Option 1)

    5

  • Option 2)

    3

  • Option 3)

    4

  • Option 4)

    2

 

Answers (1)

Let x fair coin tossed 'n' times the P( at least one head) 

=1-P ( all tail)

=1-\left ( \frac{1}{2} \right )^{n}>\frac{90}{100}

\Rightarrow \left ( \frac{1}{2} \right )^{n}<\frac{1}{10}

2^{n}>10

n\geq 4

 


Option 1)

5

Option 2)

3

Option 3)

4

Option 4)

2

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