A joke caused by decimal point

Mathematicians and their girlfriends are walking in the park. His girlfriend asked him, "Do you really mind my freckles?"

The mathematician replied softly, "Absolutely not! I was born to like dealing with decimal points. "

2. Decimal area?

The math teacher's blackboard writing is very small, but it remains the same after our repeated suggestions. In class this day, the teacher asked, "What is the area of this circle on the blackboard?" A student stood up, raised his glasses and asked doubtfully, "Does the decimal point need area?"

First, the origin of the decimal point

China has used decimal counting method since ancient times, and some practical units of measurement also use decimal, so it is easy to produce the concept of decimal. The first person to express this concept in words was Liu Hui in Wei and Jin Dynasties. In the process of calculating pi, he used seven units, such as feet, inches, minutes, centimeters, millimeters, seconds and bumps. For the following units that suddenly become smaller, they are no longer named, and they are collectively called "micro numbers".

European mathematicians didn't start to consider decimals until the 6th century/kloc-0, among which the most prominent one was Steven (1548 ~ 1620), who clearly expressed decimals in On Decimal System (1583). For example, record 5.7 14 as: 5 ◎ 7 1 1 243 or 5,7'1'4''. The first person to express decimals as a universal form in the world today is the German mathematician kravis (1537 ~ 16 12), who began to use decimal points as a separator between integer parts and decimal parts in his book Astral Chart (1593).

China adopted decimals more than 300 years earlier than Europe.

Second, the nature of decimals.

1, add or delete any zeros at the end of the decimal part, and the size of the decimal remains the same. For example: 0.4=0.400, 0.060=0.06.

2. Move the decimal point to the right (or left) by n digits respectively, and the value of the decimal point will be expanded (or reduced) by n times. (For example, the decimal is 10? )。