https://prepswift.gregmat.com/quizzes/quiz/prepswift-quant-tickbox-quiz-14-data-analysis-column-2 (Question 9)
The question mentions that “every family has a son, a daughter, both or none”, so at least one family has no son or daughter. Given that, if I use the formula I have
Since |none|>=1, wouldn’t the answer be A?
Thanks
Not really. We’ll look at how disjunctions (how the word “or” actually works) function below:
Suppose you have three categories (propositions) A, B, and C. Technically, the problem lists 4 categories, but the logic holds for any n number of categories/propositions. The following is the truth table for the “inclusive or” (the type of disjunction you’re dealing with):
\begin{array}{|c|c|c||c|}
\hline
A & B & C & A \lor B \lor C \\ \hline
T & T & T & T \\ \hline
T & T & F & T \\ \hline
T & F & …
I think that answers your question