人们在生产和生活中无时不需要测量长度,这就提出了一个长度计量单位(尺)的问题。计量单位首先要方便使用,如果这把“尺”随手可取那是再好不过了。因此,古时候人们用人身体的某个部分的长度作为长度计量单位,例如,“肘”表示伸开五指时,从肘部到中指尖的长度,“inch”(英寸)表 People do not need to measure length at all times in production and life, which raises the problem of length measurement units (feet). The unit of measurement must first be easy to use. If this is the ruler, then it would be better. Therefore, in ancient times, people used the length of a part of the human body as a measure of length. For example, “elbow” means the length from the elbow to the tip of the middle finger when extending five fingers, “inch” (inches)