We know that a coin has two sides
Sample space S = {H, T}
Total no. of outcomes = 2
It is given that a coin is tossed twice.
Consider P (A) as the probability of getting at most 1 tail
Sample space of A = {(H, H), (H, T), (T, H)}
Consider P (B) as the probability of getting a head
Sample space of B = {H}
P (B) = 1/2
So the probability of getting at most one tail and a head
(A ∩ B) = {(H, H)}
P (A ∩ B) = 1/3
Here the probability that both head and tail have appeared can be written as