Riddle: I'm always in front of you but you can never see me. What am I?
Answer: The future.
Riddle: What has eighty-eight keys but can't open a single door?
Answer: A piano.
Riddle: A man rides into town on Friday. He stays two nights. How does he leave on Tuesday?
Answer: His horse was called Friday.
Riddle: What runs without legs?
Answer: Water.
Riddle: There is a creature which could double its size every day. So, if the creature is put in a tank then it will fill the tank in 10 days. How many days would it take for the creature to fill 1/2 and 1/4 of the tank?
Answer: 9 days to fill 1/2 and 8 days to fill 1/4 of the tank.  If the creature fills the tank in 10 days and it doubles every day, on the ninth day it would fill 1/2 the tank. Thus on the 8th day it will fill 1/4 of tank.
Riddle: I have hands, but I cannot clap. What am I?
Answer: A clock!
Riddle: I go up, but I never come down. What am I?
Answer: Your age!
Riddle: Everyone has it but no one can lose it. What is it?
Answer: A shadow.
Riddle: The more you dry yourself with me the more I get wet. What am I?
Answer: A towel.
Riddle: The more you take out of me te bigger (deeper) I get. What am I?
Answer: A hole.