Question: A truck that can carry 2 tons and is is on a bridge that can support up to 2 tons. Will the bridge break?
Answer: Yes the truck is carrying 2 tons the max weight the bridge can support, but the weight of the empty truck has to be included so the truck weighs more than 2 tons.
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.