Question

Three unbiased coins are tossed together. Find the probability of getting

(i) two heads.

(ii) at least two heads.

Answer 1

Here S = {HHH, HHT, HTH, THH, TTH, THT, HTT, TTT}
(i) Favourable number of elementary events = 3          [HHT, HTH, THH]
∴ P (two heads) = 3/8
(ii) Favourable number of elementary events = 4 [HHH, HHT, HTH, THH]

∴ P (atleast two heads) =4/8=1/2