Question

A coin is tossed n times. The probability of getting head atleast once is greater than $0.8$. Then the least value of such n is

• A. $2$
• B. $3$
• C. $4$
• D. $5$

Answer 1

Answer: (B)

$3$

Probability of getting at least one head = 1-P(all tails) > $0.8$
P(all tails) < 0.2
${\left(0.5\right)}^n<0.2$
=> n is greater than equal to $3$