| Example
Tom and his wife Jenny appear in an interview for two vacancies in the
same post. The chance of Tom’s selection is 1/7 and that of Jenny’s selection
is 1/5. What is the probability that (i) both of them will be selected
(ii) only one of them will be selected
(iii) none of them will be selected.
Solution : P (Tom’s selection) = 1/7 P (wife Jenny’s selection)
= 1/5
(i) P (both selected) 
Note that when we say only Tom is selected. Simultaneously
we mean Jenny is rejected. Thus the two events become independent and hence
multiplication rule is applied . Also Tom’s selection and
Jenny’s selection in this case is a mutually exclusive. Hence finally addition
rule is applied.
(iii) P (none of them will be selected) = 
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