Question: When you talk about it, it disappears. What is it? A. A secret B. Silence C. Time
Answer: A and B. If you talk about silence then it's not silent anymore. If you talk about a secret, then other people know about it so it's not a secret anymore.
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.