Yi He Yi is the content in the math textbook of the second grade of primary school. In this regard, a math teacher said that these two units are not the current length units, but only with the help of "body size" measurement, so that students can have a more intuitive feeling of centimeters, meters and other length units, and it is also convenient to learn and understand length units.
It is the distance between two hands when an adult's arms are horizontally extended. Ancient people often used some parts of the human body as the unit of length. That's the length after you stretch your arm. Because it is impossible to carry a ruler with me at any time in life, I just started to learn length units, and I am completely unfamiliar with length units such as centimeters and meters, and I have no concept. Teaching students how to measure the length with body parts is equivalent to a body ruler.
How long is the distance between the two legs? It varies from person to person and from the size of the palm. It cannot be a fixed length. In order to let students know the length of each leg, they can measure it by themselves. Open your palm, press it on the table, pose in a fixed position, and measure forward from a certain point with the same force. For example, if you measure 5 feet, first measure the total length with a ruler, then divide it by 5 and get the average, which is your own length.