The minimum number of times one has to toss a fair coin so that the probability of observing at least one…

The minimum number of times one has to toss a fair coin so that the probability of observing at least one head is at least 90% is:
  1. 2
  2. 4
  3. 5
  4. 3

Solution

Let a fair coin is tossed n times, then
P(at least one head) =1–P(all tails)
=1–12n>90100 (given)
⇒12n<1-90100=110
⇒2n>10
⇒n≥4

Asked in: JEE Main 2019 (08 Apr Shift 2)

Practice more Probability questions on Aicharya