Alvin always tells the truth on Sundays, Tuesdays and Thursdays. He lies on every other days.  One day he said, "I told the truth yesterday."  On which day of the week did he make this statement? 
Overseas Competition->Knowledge Point->Combinatorics->Logical Reasoning
If "I told the truth yesterday" is a true statement -\/-\textgreater{} mean today I am telling the truth. But, the day that Alvin tell the truth are not consecutive day.  So, if "I told the truth yesterday" is not a true statement -\/-\textgreater{} mean yesterday I lie and today I am also lying.  Alvin lies on Monday, Wednesday, Friday and Saturday. Friday and Saturday is consecutive day he lies, so it must be Saturday. 