Question: You have a bag with 'N' strings in it. You randomly grab two ends and tie them together until there are no more loose ends.
In the end, what is the expected number of loops (strings tied to their own end)?
Answer: 1 + 1/3 + 1/5 ... + 1/(2N-1).
Each time you tie two together the number of string ends available decreases by 2. The chance of grabbing a string and its end is 1/(2N-1).
Question: One day a man broke his leg. When he was sent home from the hospital he had to use a wheelchair. The doctors told him he could not go up stairs. When the man got home he realized he had stairs to get into his house on both sides. The man saw his neighbor, the doctor who x-rayed him at the hospital, getting out or her car. The man asked "can you carry me up the stairs?" The woman replied "no." Why?
Answer: She told the man he could not go up stairs
Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?
The glass is a right cylinder.
Answer: Tip the glass of water until the water reaches the rim of the glass and if the water lines up perfectly with the bottom rim of the glass, it is half full.