Tossing of coins

Two coins are tossed simultaneously. Find the probability of getting two tails if it is known that there is at least one tail.

Sol:

The sample space (S) consist of = (HH, HT, TH, TT)

Let A be the event of getting at least one tail.

The sample space of A = (HT, TH, TT)

⇒ n(A) = 3

Let B be the event of getting two tails.

Sample space of B = (TT)

Sample space of (A ∩ B) is also = (TT)

⇒ n(A ∩ B) = 1

B/A is the event of occurrence of event B after event A has occurred.

∴