Logic
# Truth-Tellers and Liars

A self-referential statement is a statement that describes itself.

Is the following self-referential statement true?

$\begin{array}{|l|} \hline {\text{ Seven words are used in this sentence. }} \\ \hline \end{array}$

$\begin{array}{|l|} \hline {\text{This statement is false. }} \\ \hline \end{array}$

If the statement above is logical, can we conclude that the statement is indeed false?

If this statement has eleven words, then this statement is false.

If the statement above is logical, can we conclude that the statement is indeed false?

Assuming this self-referential statement is logical, determine whether it is true or false.

$\begin{array}{|l|} \hline {\text{ This statement is either true or false. }} \\ \hline \end{array}$

If Haley speaks every day, only tells lies on the weekends (Saturday and Sunday) and only tells the truth on all other days, on which days can she make the following statement?

"I told a lie yesterday."