Three unbiased coins are tossed. What is the probability of getting at least 2 tails?

Solution (By Examveda Team)

S = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}
E = {HTT, THT, TTH, TTT}
$$\eqalign{ & {\text{n(S) = 8}} \cr & {\text{n(E) = 4}} \cr & {\text{P(E) = }}\frac{{{\text{n(E)}}}}{{{\text{n(S)}}}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{\text{4}}}{8} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{0}}{\text{.5}} \cr} $$