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?
You are walking down a path when you come to two doors. Opening one of the doors will lead you to a life of prosperity and happiness, while opening the other door will lead to a life of misery and sorrow. You don't know which door leads to which life.
In front of the doors are two twin brothers who know which door leads where. One of the brothers always lies, and the other always tells the truth. You don't know which brother is the liar and which is the truth-teller.
You are allowed to ask one single question to one of the brothers (not both) to figure out which door to open.
What question should you ask?
Ask "If I asked your brother what the good door is, what would he say?"
If you ask the truth-telling brother, he will point to the bad door, because this is what the lying brother would point to.
Alternatively, if you ask the lying brother, he will also point to the bad door, because this is NOT what the truth-telling brother would point to.
So whichever door is pointed to, you should go through the other one.