1, egg problem: Xiao Zhang sells eggs, a basket of eggs, the first person buys half, and then gives him another one. The second man bought another half, and Xiao Zhang gave him another egg. The third man bought another half egg, and Xiao Zhang gave him another one. The fourth man came to buy half, and Xiao Zhang gave him another one, just after buying the eggs! How many eggs has Xiao Zhang always had?

2, the table problem, a square table, how many corners are there after cutting off a corner?

3, cut tofu problem: a piece of tofu cut three knives, how many pieces can you cut at most?

4, cut watermelon problem: three knives cut 7 petals, eat the remaining 8 skins, how to cut?

5. Bamboo pole problem: Can a 5-meter-long bamboo pole pass through the 1 meter-high door?