Math puzzles

1 Suppose there is a pond with infinite water in it. There are currently 2 empty kettles with a capacity of 5 liters and 6 liters respectively. The problem is how to get 3 liters of water from the pond using only these 2 kettles.

2 Zhou Wen’s mother is a laboratory technician at a cement factory. One day, Zhou Wen came to the laboratory to do homework. I want to go out and play after I'm done. "Wait a minute, mom has another question for you." She continued, "Look at these 6 test glasses, the first 3 are filled with water, and the last 3 are empty. Can you move only 1 Glass, just separate the filled cup and the empty cup?" Zhou Wen, who loves to use her brain and is a famous "little clever" in the school, did it after just thinking about it for a while. Please think about it, what does "Little Clever" do?

3 Three young men fell in love with a girl at the same time. In order to decide which of them could marry the girl, they decided to have a duel with pistols. Xiao Li's hit rate is 30%, Xiao Huang is better than him, his hit rate is 50%, the best shooter is Xiao Lin, he never makes mistakes, his hit rate is 100%. Because of this obvious fact, for the sake of fairness, they decided to go in this order: Xiao Li shot first, Xiao Huang second, and Xiao Lin last. And then cycle like this until they only have one person left. So who among these three has the best chance of survival? What strategies should they all adopt?

4 There are two prisoners in a cell. Every day, the prison provides a can of soup to this cell, allowing the two prisoners to divide it among themselves. At first, the two people often quarreled because one of them always thought that the other party had more soup than their own. Later, they found a way to get the best of both worlds: one person divided the soup and let the other person choose first. So the dispute was settled. However, now a new prisoner has entered this cell, and now there are three people sharing the soup. A new way must be found to maintain peace between them. What to do?