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.
Question: When Tommy was 10 years old his sister Suzy was half his age. Now that Tommy is 50 years old how old is his sister Suzy?
Answer: 45 years old. Suzy was 5 when Tommy was 10 so she is 5 years younger.