What do the numbers on the tape measure stand for?

The numbers on the tape measure are divided into two lines. The unit of one line is cm/cm, and the unit of the other line is inch. 1CM is about 0.3937 inch, and 1cm is about =2.54CM, so the shorter unit of the two numbers is cm and the longer one is inch. Digital fonts in centimeters are also smaller than those in inches, 100 cm = 1 m, and the commonly used unit is centimeters.

Tape measure is a common measuring tool in daily life. Steel tape measure is often used in construction and decoration, and it is also one of the necessary tools for families. Tape measure is divided into fiber tape measure, tape measure, waistline measure and so on. Lu Banchi, Feng Shui ruler and secretary also belong to steel tape measure. The specifications of tape measure are 1m, 1.5m, 2m, 3m, 5m, 7.5m, 8m, 10m, 20m, 30m, 50m, 100m.

3m, 5m, 7m, 10m are commonly used, 30m and 50m are rarely used, and 5m and 10m are more commonly used because of their small size and convenient carrying.

Inventor of tape measure

The inventor of the world's first tape measure was Cheng Dawei, a famous mathematician, abacus operator and inventor in Ming Dynasty. He invented it around 1578. He called it "measuring walking bicycle" at that time, so Cheng Dawei was called "the father of tape measure". Compared with the existing steel tape and leather tape, the "measuring device" is much larger, but from its principle, structure, use and usage, it is the prototype of tape measure.

It consists of a wooden coat, a cross, a bamboo ruler, an iron swivel, a drill foot and a ring. The rod ruler is put in and taken out from the plate hole of the jacket, which is convenient for the drilling foot to be accurately inserted into the field measurement point and easy to carry. Prior to this, "the ancients measured the field wider and longer, and measured it completely by rope ruler", which was not only labor intensive, but also had a high error rate.

The value of Cheng Dawei lies in the inspiration of replacing the rope with a flat ruler. This revolutionary achievement has been strictly enjoyed by tape measure until now.

Cheng Dawei birthday Dao

1533, Cheng Dawei, born in Anhui during Jiajing period of Ming Dynasty. Relevant historical records even record that Cheng Dawei has been an official for generations, achieving the high position of the satrap. However, during the Jiajing period, foreign thoughts began to surge and people's thoughts became active. More and more people are beginning to abandon their official positions and go into business, and the Cheng family is no exception.

The Cheng family, who has been an official for generations, has gathered people's hearts in Xiuning, Anhui Province and has relatively rich wealth. Cheng Dawei, who had been dealing with businessmen since childhood, also had an inexplicable love for numbers, which laid the foundation for his future research in arithmetic.

What is the most important thing in doing business? The most important thing is to make money. Making money is not just a few stacks of money. In the feudal era without computers and banks, the calculation, use and preservation of money was a headache.

In fact, as early as the Sui and Tang Dynasties, China began to strengthen mathematics education in schools, because from astronomical geography to water conservancy projects, to be more specific, people were required to buy food and pay for it.

At the beginning, most of our civil and military officials in the past dynasties focused on planning, and their specific operation method was to calculate and check with small bamboo sticks with numbers.

The Ming emperors paid more attention to the artificial study of Neo-Confucianism and Confucian classics, but not enough attention to natural subjects such as mathematics and physics, which led to the decline of traditional arithmetic technology. As a traditional agricultural country, China cannot do without digital counting.

What's more, although the traditional calculation has been used for a long time, it faces the natural disadvantages of poor operation and slow calculation speed. Under the internal pressure of outmoded calculation methods and the external pressure of laissez-faire in the Ming Dynasty, Cheng Dawei officially began to reform the calculation methods, and this reform measure is still in use today.