How many times must a man toss a fair com so that the probability of having at least one head is more than 90%?

Explanation

Let `n` times a coin must be tossed so that probablity of having at least one head is more than `90%`.

`P(`At least one head`) = 1-P(`All tail`)`

`=>1-(1/2)^n > 90/100`

`=>(1/2)^n >=0.1`

Adding log base 10, to both sides,

`n(log1 - log2) > -1`

`-nlog2 > -1`

`n>1/log2=>n >1/0.3=>n>3.33`

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