Two coins are tossed together. What is the probability of getting :

(i) at least one head ?

(ii) both heads or both tails ?

When two coins are tossed together, the total number of possible outcomes = 4 (i.e. HH, HT, TH and TT)

(i) Number of favourable outcomes (Getting at least one head) = 3 (HT, TH and HH)

P(Getting at least one head) = $\dfrac{\text{Number of favourable outcomes}}{\text{Total number of outcomes}}$

= $\dfrac{3}{4}$

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

(ii) Number of favourable outcomes (Getting both heads or both tails) = 2 (HH and TT)

P(Getting both heads or both tails) = $\dfrac{\text{Number of favourable outcomes}}{\text{Total number of outcomes}}$

= $\dfrac{2}{4}$

= $\dfrac{1}{2}$

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