You are looking at somebody's photo. Who is it you are looking at, if you don't have any brother or sister and father of that man on the photo is the son of your father?
These are true statements about inhabitants of a town.
1. No two inhabitants have the same number of hair on their head 2. No inhabitant has exactly 518 hairs 3. There live more inhabitants than any inhabitant's hair in the town
What is the highest possible number of inhabitants?
How can you throw a ball as hard as you can and have it come back to you, even if it doesn't hit anything, there is nothing attached to it, and no one else catches or throws it?
A table tennis ball fell into a tight deep pipe. The pipe was only a bit wider then the ball, so you can not use your hand. How would you take it out, with no damage?