Mark the correct alternative in the following:

A coin is tossed n times. The probability of getting at least once is greater than 0.8. Then, the least value of n, is

Given:

P(H)=P(T)=1/2

P(H)= H^{1}T^{n-1}+H^{2}T^{n-2}+H^{3}T^{n-3}+…..+H^{n-1}T^{1}+H^{n}

Required probability = p= 1-

P0.8

For n= 2

For n=3

So, n=3

1