Last Problem
You’ve driven into a the country of
Black & White where there are (truthfully)
only truth tellers and liars. There is no
middle ground. No one can tell the
difference by looking a man or woman
straight in the eyes.
This is a dangerous trip and you must make
good decisions. There is no room for mistakes.
While traveling down Route 66 you come to
a fork in the road. One way leads to safety.
The other way to a terrorist attack.
The sign post is gone at the fork, but there
are two men standing at the fork waiting for
a bus. One man has a white beard. The other
has green eyes.
What question can you ask either man that
will tell you which road is safe?
Answer:
The question to be asked is:
“Which road would the other man tell me is safe?”
Both men will tell you the unsafe road – so take
the other one.
The truth teller would say the liar will lie
and tell you the unsafe road is safe. The liar
will tell you that the truth teller will say
opposite of the truth and thus tell you the
unsafe road.
Today’s Problem
What is the next entry in this sequence? -2 4 -12 48 -240