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Three coins are tossed once. Let $A$ denote the event ' three heads show ', $B$ denote the event ' two heads and one tail show ' , $C$ denote the event ' three tails show and $D$ denote the event 'a head shows on the first coin '. Which events are mutually exclusive ?
Solution
When three coins are tossed, the sample space is given by
$S =\{ HHH ,\, HHT , \,HTH ,\, HTT , \,THH ,\, THT , \,TTH , \,TTT \}$
Accordingly,
$A=\{H H H\}$
$B =\{ HHT ,\, HTH ,\, THH \}$
$C =\{ TTT \}$
$D =\{ HHH , \,HHT , \,HTH , \,HTT \}$
We now observe that
$A \cap B$ $=\phi, A \cap C$ $=\phi, A \cap D$ $=\{H H H\} \neq \phi$
$B \cap C=\phi, B \cap D$ $=\{H H T,\, H T H\} \neq \phi$
$C \cap D=\phi$
Event $A$ and $B$ ; event $A$ and $C$; event $B$ and $C$; and event $C$ and $D$ are all mutually exclusive.
