5. Three coins are tossed. Describe
(v) Three events which are mutually exclusive but not exhaustive
Sample space when three coins are tossed = [Sample space when a coin is tossed thrice!]
S = {HHH, HHT, HTH, HTT, THH, TTH, THT, TTT}
Let ,
A = Getting exactly one tail = {HHT, HTH, THH}
B = Getting exactly two tails = {HTT, TTH, THT}
C = Getting exactly three tails = {TTT}
Clearly, A B = ; B C = ; C A =
Since (A and B), (B and C) and (A and C) are mutually exclusive
Therefore A, B and C are mutually exclusive.
Also,
A B C = {HHT, HTH, THH, HTT, TTH, THT, TTT} S
Hence A, B and C are not exhaustive events.