The minimum number of times a fair coin needs to be tossed, so that the probability of getting at least two heads is at least 0.96 is :

Explanation

Let coin be tossed n times.
P (at least two heads) = 1 - P (no heads) - P (exactly one head)
P (at least two heads) `=1-((1)/(2))^(n)-""^(n)C_(1).((1)/(2))^(n)ge0.96`
`implies4/100ge(n+1)/(2^(n))`
`implies(2^(n))/(n+1)ge25`
Therefore, least value of n is 8.