What are the math stories? About 20-30 words

What are the math stories? About 20-30 words

The symbol "+" - "was first used by a German 500 years ago. At that time, they did not mean" plus "or" minus ". It was more than 300 years ago that it was officially used to mean" plus "or" minus "
2. "Tangram" is a kind of jigsaw puzzle in ancient China. It is composed of seven pieces that can be put together into a large square sheet, and the pattern changes a lot. Later it was spread abroad as "tangtu". Today, Tangram has become a kind of popular intellectual game
3. It is said that as early as four or five thousand years ago, our ancestors used a kind of dripping instrument to time, which is called carve leak
4. The multiplication sign "×" was first used by an English mathematician more than 300 years ago. Because multiplication is a special addition, he diagonally expressed the plus sign
5. In 46 BC, Julius Caesar, the commander of Rome, appointed the calendar. Because he was born in July, in order to show his greatness, he decided to change July to "Julius month", and all single months were set as 31 days, and double months were set as 30 days. In this way, there was one more day in a year. February was the month of execution in ancient Rome. In order to reduce the number of execution, February was reduced by one day to 29 days
6. Xiao Fang is a carpenter, but he is very arrogant. One day, the master asked him, "the table has four corners, I cut off one, how many are left?" Xiao Fang said 4-1 = 3, three. The master told him that there are five