A coin is successively tossed two times. Find the probability of getting? (1) exactly one head (2)at least one head

In tossing a coin 2 times the sample space is 4 i,e (H, H), (H, T), (T, H), (T, T)
(1) If A₁ denotes exactly one head
then A₁ = {(H, T) (T, H) }
So, P(A₁ ) = 2/4 = 1/2
(2) If A denotes at least one head
then A = {(H, T) (T, H) (H, H)}
∴ A = {(H, T) (T, H) (H, H )}
∴ P(A) = 3/4