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Does anybody know where I can find some really challenging deductive logic puzzles? They're so much fun to solve and I can't find any. Thanks.

Two words; Rubics cube. Really challenging. And if you tell me that you can solve one in under two minutes, I'll pour mustard in your piano.

RubiKs cube. Heh.

Really challenging logic puzzles? I'm afraid I don't have any... calculus is enough puzzling for me...

Have you tried Dover? http://store.doverpublications.com/by-subject-puzzles--amusement--recreations-general.html

You could pick up a book of Mensa puzzles; there are probably quite a few of those around. Some of the logic problems in these books are easy, but others are quite difficult. Here are a few examples of logic problems you'd find in these books:

1. In an election for class president, John is competing with two other candidates. After the election, the votes were tallied and it was found that each of the three candidates received exactly the same number of votes. However, there are rules that there could only be one president, and to settle this situation the three candidates agreed to draw a name out of a bag to determine who was going to be the winner. John takes a fresh piece of paper, writes one of the other candidates' names on the upper part of the sheet, his name in the middle, and the third candidate's name on the lower part of the sheet. He then tears the sheet of paper into strips so that each strip contains the name of one candidate. He places each of the strips into a bag and volunteers to draw the name of the winner. How does he ensure that he wins the election even though he is very adequately blindfolded?

2. A spy was captured by the enemy and was scheduled to be executed. Before the spy would be killed, he had the chance to make only one statement; if he told the truth, he would be hanged, and if he told a lie, he would be shot. The spy makes his statement, and afterwards, the enemy soldiers debate for hours about what to do and eventually decide to set the spy free. What did the spy say? (A very farfetched and unrealistic situation, but an excellent logic puzzle nonetheless.)

3. You have just left Venice and must travel to Rome by way of a desolate path that wanders through a thick forest. You travel down the path and come to a four-way intersection. There is a signpost that points the way to Rome and also points the way to Venice, but the signpost has been uprooted and is lying on the ground. There is nobody around for miles to ask for directions and you have no map or compass, and the night is cloudy so you are unable to look up into the sky to find the North Star. How do you figure out which path to take?

(Have fun trying to figure out the answers to these.)

Starve to death.

Seriously, though...go the opposite way that the sign is pointing to.

He feels for the strip with two ripped sides (the middle strip has his own name on it).

He says, "What I am about to say is the truth that is: what I have just said is a lie". You're right. Unrealistic. I would shoot the SOB anyway.

Correct.

Close. But the answer I was looking for was a sentence of only four words.

Thanks. I'll work on those, plus I'll visit that web site. In the meantime, heres one for the rest of you. Its fairly easy:

A man looks at a picture and says "Brothers and sons, I have none. But the father of this person is my fathers son." Who is he looking at in the picture?

He is looking at his daughter. He says he has no brothers, therefore, if the father of the person in the picture is his father's son, he must be the father of the person in the picture since he is the only person that would be eligible to be "his father's son." He has no sons, so the person in the picture is his daughter.

NOPE! Thats what I thought the first time that I read it, but its wrong. Read the clues a bit more carefully and think about them, and it will come to you. It took me a while, but I got the correct answer myself, and without looking at it first.

You told us the riddle wrong, jgoo. It's supposed to be "Brothers and sisters, I have none," not "Brothers and sons."

He is looking at a picture of himself.

"I'LL KILL YOU ALL!!!!!!!!"

Maybe you could examine the signpost for moss. If there is moss growing on the signpost it will be on the north side. Unless you are in Oregon, in which case it grows on all sides, and you are dead.

"This is a lie" or "I am now lying" or something to that effect.

"I will kill you" should get him hung since it is a true statement of his intentions no matter whether it is actually possible. In other words, it may be false but that does not make it a lie.

I assume that the signs to Venice and to Rome are attached to the same post. In that case I'd just plant the signpost into the ground with the sign to Venice pointing to where I came from. The sign to Rome should now correctly point to Rome.

I actually thought of this but can it really be that easy? I assumed there was something I was not understanding correctly about the problem. It just does not seem like a very difficult problem if this is correct.

The guy who was (or was not) going to be shot might have said: "I will be released". If true, he gets to leave, if false, he's shot. Either way, the problem is solved. This is the only thing I can think of that would cause hours of discussion on the part of his captors.

I agree with the solutions of the other problems as given.