If two coins are tossed once, what is the probability of getting :

(i) 2 heads ?

(ii) at least one head ?

(iii) both heads or both tails ?

When two coins are tossed,

Possible outcomes = {HH, HT, TH, TT}.

No. of possible outcomes = 4.

(i) Favourable outcomes for getting 2 heads = {HH}.

No. of favourable outcomes = 1.

P(getting 2 heads) = $\dfrac{\text{No. of favourable outcomes}}{\text{No. of possible outcomes}} = \dfrac{1}{4}$.

Hence, the probability of getting 2 heads = $\dfrac{1}{4}$.

(ii) Favourable outcomes for getting at least one head = {HT, TH, HH}.

No. of favourable outcomes = 3.

P(getting at least one head) = $\dfrac{\text{No. of favourable outcomes}}{\text{No. of possible outcomes}} = \dfrac{3}{4}$.

Hence, the probability of getting at least one head = $\dfrac{3}{4}$.

(iii) Favourable outcomes for getting both heads or both tails = {HH, TT}.

No. of favourable outcomes = 2.

P(getting both heads or both tails) = $\dfrac{\text{No. of favourable outcomes}}{\text{No. of possible outcomes}} = \dfrac{2}{4} = \dfrac{1}{2}$.

Hence, the probability of getting both heads or both tails = $\dfrac{1}{2}$.