Question

If a coin is tossed two times, what is the probability of (i) Getting head at least once? (ii) Getting exactly one head?

Answer 1

In tossing a coin twice, there are 4 possible outcomes, they are
{TT,HT, TH, HH}
(1) getting at least 1 head:

Let E1 = event of getting at least 1 head. Then,
E1 = {HT, TH, HH} and,
therefore,
n(E1) = 3.
Therefore,
P(getting at least 1 head) = P(E1) = n(E1)/n(S) =3/4

(2)getting exactly one head
let E2=event of getting exactly one head
E2= {HT, TH}
n(E2)=2
P(getting exactly 1 head) = P(E2) = n(E2)/n(S) = 2/4=1/2