The New Sudoku Players' Forum

[Laura]

Hi, I'm Laura and I like sudoku.
I like all kinds of brain teasers
and logic puzzles. Anyone here into
3-D puzzles?

[Smythe Dakota]

I'm not really into 3-D, except to observe that 3-D tic-tac-toe, unlike 2-D, is a forced win for the first player.

Here's one you've probably already heard:

You are in a room with two doors. One door leads to freedom. The other door leads to a lion who will immediately eat you as soon as you open the door. You don't know which door is which. There are two guards in the room. One of them always tells the truth. The other always lies. You don't know which is which. You are allowed to ask one question of one of the guards. What question should you ask, so that you will know which door you should open?

Bill Smythe

[tarek]

You'll love 'The Curse'

This is a riddle from their Valentine special:

Roses are red
Violets are blue
Add a daffodil
And answer this clue

[daj95376]

Assuming that both guards know what's behind both doors, and that each guard knows the false/true nature of the other guard.

Question: Which door would the other guard recommend that I enter?

You then enter the door not in the reply!

[7b53]

hehe.....beside knowing which door is safe, you should also know which guard is a liar.
the new question is.....

[Smythe Dakota]

I doubt very much whether you could find a single question asked of one guard that would tell you both which door is safe and which guard is lying.

Bill Smythe

[7b53]

Bill,
I don't even have an answer. but pretty sure there is one, because I clearly remember this problem.
since daj already posted half of the answer(question). we can just concentrate on the other part.
"what question will tell us which is the lying guard".
then try to combine it with daj's answer to figure out the new question.

[Smythe Dakota]

Well, of course you could always ask, "which guard would the other guard say is the liar?" and either guard would point toward the truth-telling guard. This is similar to the original answer. But I still don't see how you could combine both into one question, without making it a compound question, which in essence would be two questions.

Bill Smythe