Easy math one: Usain Bolt was challenged by a turtle to a race. Usain gladly accepted; then the wise old turtle twisted the rules. While the turtle can walk nonstop, Usain Bolt must run half the distance he covered, pause five seconds, and proceed. After thinking for a while, Bolt resigned and let the turtle win. Why?
Challenging: I bet that you alone cannot take your shoes off while I am present. If I don't interfere with your actions, how do I prevent you?
Post riddles or puzzles here and people can try to solve them.
Here is one: None are jumping down over red field.