For a field of one mu, the width is 15 bu. If we space it out, it becomes 15 rows, where each row has a width of 1 bu and a length of 16 bu. If we then cut across it horizontally, it becomes 16 rows, where each row has a width of 1 bu and a length of 15 bu. This means the length-spaced and width-cut steps each form a square. There are 240 bu in one mu of land; the number of paces is exactly the same. Speaking from this, multiplying width and length to obtain the area is verified. 240 bu is the method for mu. 100 mu is the method for qing. Therefore, by dividing by these, one obtains the result.

Now, there is a field with a width of 1 li and a length of 1 li. How much is the field?
Answer: 3 qing and 75 mu.

There is another field with a width of 2 li and a length of 3 li. How much is the field?
Answer: 22 qing and 50 mu.

Fields measured in li