Three people go for 30 yuan a night. Each of them paid 10 yuan enough. 30 yuan gave it to the boss. Later, the boss said that 25 yuan was enough for today's discount, so he took out the 5 yuan and asked the waiter to return it to them. The waiter secretly hid 2 yuan's money, and then distributed the rest of 3 yuan's money to three people, each with 1 yuan.

In this way, at the beginning, everyone paid 10 yuan, and now it is returned to 1 yuan, that is, 10- 1 = 9. Everyone only spent 9 yuan's money, three people spent 9 yuan, 3X9=27 yuan+2 yuan hidden by the waiter = 29 yuan. Where did the dollar go?

2. Controversy in the field of mathematics: Zeno Paradox.

This is also a controversy in the field of physics. Achilles and Zhi Nuo the tortoise ran together. Before Achilles started running, the tortoise was 65,438+000 meters ahead of Alisky.

Achilles runs 100 meter, the tortoise runs one meter more, Achilles runs one meter, and the tortoise runs one centimeter more. It can be inferred that Achilles will never outrun the tortoise. Although it runs very fast in reality, it seems that it will never catch up with it in mathematics.

3. Strange math problems: ants and rubber bands

An ant is crawling from one end of the rational elastic rope to the other at a speed of 1cm per second. The elastic rope is stretched uniformly at the speed of 1m per second. Can ants climb to the finish line?

It doesn't look very useful, but it works in mathematics. Assuming that the speed of the elastic rope is 0.9 cm per second, ants can intuitively climb to the finish line. The uniform elongation of the elastic rope means that there is always a point on it with a speed of 0.9 cm per second, which means that ants can climb to this point. Next, just segment the whole elastic rope.