Good Riddles

Question: You need a room for your group. Each person needs 5 square feet of space. You have 25 people in your group, what is the smallest room you can use?

Question: Something you know nobody knows, and everyone knows something you don't. We all know something, nobody knows everything, and you know something someone doesn't know. What else could nobody know?

Question: Have a question , regardless you ask any people , that people only give you answer is " no " , what is this question ??

Question: A child asked his grandfather: "When you were young, what were you?" The grandfather replied, "I am one hundred, nothing, one thousand, one and one hundred". What's his career?

Question: I am a 3 letter word spelled with 3 different letters, and if you reverse the spelling of the word, it will sound the same. What word am I?