You are standing before two doors. One of the path leads to heaven and the other one leads to hell. There are two guardians, one by each door. You know one of them always tells the truth and the other always lies, but you don’t know who is the honest one and who is the liar. You can only ask one question to one of them in order to find the way to heaven. What is the question?
The question you should ask is "If I ask the other guard about which side leads to heaven, what would he answer?"
It should be fairly easy to see that irrespective of whom do you ask this question, you will always get an answer which leads to hell. So you can chose the other path to continue your journey to heaven.
This idea was famously used in the 1986 film Labyrinth.
Here is the explanation if it is yet not clear.
Let us assume that the left door leads to heaven.
If you ask the guard which speaks truth about which path leads to heaven, as he speaks always the truth, he would say "left". Now that the liar , when he is asked what "the other guard (truth teller) " would answer, he would definitely say "right".
Similarly, if you ask the liar about which path leads to heaven, he would say "right". As the truth teller speaks nothing but the truth, he would say "right" when he is asked what "the other guard( liar ) " would answer. So in any case, you would end up having the path to hell as an answer. So you can chose the other path as a way to heaven.
While mixing sand, gravel, and cement for the foundation of a house, a worker noticed a small bird hopping along the top of the foundation wall. The bird misjudged a hop and fell down one of the holes between the blocks. The bird was down too far for anyone to reach it and the hole was too small for it to fly out of. Someone suggested using two sticks to reach down into the hole and pull the bird out, but this idea was rejected for fear it would injure the fragile bird. What would be the easiest way to get the bird out of the hole without injuring it?
Since they had plenty of sand available, they could pour a little at a time into the hole. The bird would constantly keep shifting its position so that it stood on the rising sand.
Betty signals to the headwaiter in a restaurant, and says, "There is a fly in my tea."
The waiter says "No problem Madam. I will bring you a fresh cup of tea."
A few minutes later Betty shouts, "Get me the manager! This is the same cup of tea."
How did she know?
Hint: The tea is still hot.
Betty had already put sugar in her tea before sending it back. When the "new" cup came, it was already tasted sweet.
A man is sitting in a pub feeling rather poor. He sees the man next to him pull a wad of £50 notes out of his wallet.
He turns to the rich man and says to him, 'I have an amazing talent; I know almost every song that has ever existed.'
The rich man laughs.
The poor man says, 'I am willing to bet you all the money you have in your wallet that I can sing a genuine song with a lady's name of your choice in it.'
The rich man laughs again and says, 'OK, how about my daughter's name, Joanna Armstrong-Miller?'
The rich man goes home poor. The poor man goes home rich.
What song did he sing?
Mr. Black, Mr. Gray, and Mr. White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr. Black, who hits his shot 1/3 of the time, gets to shoot first. Mr. Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr. White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. All three competitors know one another's shooting odds. If you are Mr. Black, where should you shoot first for the highest chance of survival?
He should shoot at the ground. If Mr. Black shoots the ground, it is Mr. Gray's turn. Mr. Gray would rather shoot at Mr. White than Mr. Black, because he is better. If Mr. Gray kills Mr. White, it is just Mr. Black and Mr. Gray left, giving Mr. Black a fair chance of winning. If Mr. Gray does not kill Mr. White, it is Mr. White's turn. He would rather shoot at Mr. Gray and will definitely kill him. Even though it is now Mr. Black against Mr. White, Mr. Black has a better chance of winning than before.
One day a scholar came to the court of Emperor Akbar and challenged Birbal to answer his questions and thus prove that he was as clever as people said he was.
He asked Birbal: "Would you prefer to answer a hundred easy questions or just a single difficult one?"
Both the emperor and Birbal had had a difficult day and were impatient to leave.
"Ask me one difficult question," said Birbal.
"Well, then tell me," said the man, "which came first into the world, the chicken or the egg?"
"The chicken," replied Birbal, very confidently.
"How do you know?" asked the scholar, a note of triumph in his voice.
What did Birbal answer to this?
Birbal told the scholar, "We had agreed you would ask only one question and you have already asked it" and he and the emperor walked away leaving the scholar gaping.
A group of campers have been on vacation so long, that they've forgotten the day of the week. The following conversation ensues.
Darryl: "What's the day? I dont think it is Thursday, Friday or Saturday."
Tracy: "Well that doesn't narrow it down much. Yesterday was Sunday."
Melissa: "Yesterday wasn't Sunday, tomorrow is Sunday."
Ben: "The day after tomorrow is Saturday."
Adrienne: "The day before yesterday was Thursday."
Susie: "Tomorrow is Saturday."
David: "I know that the day after tomorrow is not Friday."
If only one person's statement is true, what day of the week is it?