Originally posted by Seifer28:
Garfield is a strange liar. He lies on six days of the week, but on the seventh day he always tells the truth. He made the following statements on three successive days:
Day 1: I lie on Monday and Tuesday.
Day 2: Today, its Thursday, Saturday or Sunday.
Day 3: I lie on Wednesday and Friday.
On which day does Garfield tell the truth????
If the statement on day 1 is untrue = he tells the truth on Monday or Tuesday.
If the statement on day 3 is untrue = he tells the truth on Wednesday or Friday.
Since Garfield tells the truth on only one day = cannot both be untrue.
Assume that the statement on day 1 is true.
Then the statement on day 3 must be untrue, from which follows that Garfield tells the truth on Wednesday or Friday.
So, day 1 is a Wednesday or a Friday. Therefore, day 2 is a Thursday or a Saturday.
However, this would imply that the statement on day 2 is true, which is impossible. From this we can conclude that the statement on day 1 must be untrue.
Assume that Garfield told the truth on day 3 and that this day is a Monday or a Tuesday. So day 2 is a Sunday or a Monday. Because the statement on day 2 must be untrue --> day 2 = Monday.
So day 3 is a Tuesday. Therefore, the day on which he tells the truth is Tuesday.
