Question 1138445
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This conditional probability can be calculated in two ways:


    a)  As a conditional probability  {{{((12/70))/((42/70))}}} = {{{12/42}}} = {{{2/7}}},   


or directly, based on common sense (and even without knowing the formal definition of probability, at all), as


    b)  {{{12/42}}} = {{{2/7}}}.


Both answers are the same.


Notice that the given part of the condition 

    "26 secretaries are employed by the firm"

is not used in the solution and is excessive and unnecessary.


It is included into the condition with the only goal to confuse a reader and to check if he (or she) knows the subject.
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Solved, answered and completed.