The least number of times a fair coin be tossed so that the probability of having atleast one head is more than 80% is :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 3
$\text{P(at least one head) = 1 - P(No heads)}$
$⇒1-(\frac{1}{2})^n>0.80$
$⇒(\frac{1}{2})^n<0.20$
$⇒n>2.32$
∴ The least number of tosses required is 3.