One fellow (A
) lies only on Mondays, Tuesdays, and Wednesdays, and tells the truth on other days, and his friend (B
) lies on Thursdays, Fridays, and Saturdays, and tells the truth on other days.
At noon, they have the following conversation:
A: I lie on Saturdays.
B: I will lie tomorrow.
A: I lie on Sundays.
On which day of the week does this conversation take place?
Adapted from Crux Mathematicorum.
A's first statement is a lie, so we know it's either Monday, Tuesday or Wednesday. B tells the truth on those days, so his claim that he'll lie tomorrow means it must be Wednesday. We don't need A's second statement (though of course it is also a lie, which is consistent with the answer).
Posted by tomarken
on 2016-04-21 08:10:49