I thought it would be interesting to start a thread devoted to posing and dissecting riddles and brainteasers. Yeah, so I'm a pretty huge nerd.
You can most likely find the solution to any of the riddles and brainteasers people post here on the Internet, but that sort of ruins the fun now doesn't it? The first two riddles I will post here I came across surfing the Internet, matter a'fact, but you have my solemn oath I've not looked at the solutions, nor will I look for the solutions to any riddles subsequently posted in this thread before commenting upon them. Let's make that the code of conduct for this thread. Anyone who is clearly in violation of this code of conduct will have to live knowing that strangers on the Internet think he's a real fat jerk, so there.
The solution is here. See how closely your thinking matches!The Monty Hall Problem:
Suppose you're on a game show and you're given the choice of three doors. Behind one door is a car; behind the others, goats. The car and the goats were placed randomly behind the doors before the show. The rules of the game show are as follows: After you have chosen a door, the door remains closed for the time being. The game show host, Monty Hall, who knows what is behind the doors, now has to open one of the two remaining doors, and the door he opens must have a goat behind it. If both remaining doors have goats behind them, he chooses one randomly. After Monty Hall opens a door with a goat, he will ask you to decide whether you want to stay with your first choice or to switch to the last remaining door. Imagine that you chose Door 1 and the host opens Door 3, which has a goat. He then asks you "Do you want to switch to Door Number 2?" Is it to your advantage to change your choice?
Next is a riddle I found on an IQ test of somewhat questionable validity:
Taking this riddle at face value, it can be solved pretty quickly, but it has one rather large flaw. In order to test whether or not my thinking is solid, I'm curious to see if other members spot the same flaw.Bob is locked in a crappy dungeon with three doors, all with signs posted on them. He knows that behind one of the doors is freedom, and behind the other two doors are dragons (which will brutally maul him, because that's what they do). He also knows that at least one of the signs is telling the truth, and that at least one of the signs is lying. The signs read:
Door 1: Freedom is not behind this door.
Door 2: Freedom is not behind this door.
Door 3: Freedom is not behind the blue door.
He thinks for a second and then leaves through door number 3. Which is the blue door?
Edit: in the name of fairness, I'll confess that people may find my issue with this riddle to be either flippant or pedantic, depending upon their assessment of my character.
Finally, the classic two guards riddle:
Many people are likely familiar with the proper answer, but to make this more of a challenge: imagine that you are only allowed to ask one guard one yes or no question only.You stand at a fork in the road. Next to each of the two forks, there stands a guard. You know the following things: 1. One path leads to Paradise, the other to Death. From where you stand, you cannot distinguish between the two paths. Worse, once you start down a path, you cannot turn back. 2. One of the two guards always tells the truth. The other guard always lies. Unfortunately, it is impossible for you to distinguish between the two guards.
You have permission to ask one guard one question to ascertain which path leads to Paradise. Remember that you do not know which guard you're asking -- the truth-teller or the liar -- and that this single question determines whether you live or die. The question is: What one question asked of one guard guarantees that you are led onto the path to Paradise, regardless of which guard you happen to ask?