If a number be measured by any number, the number which is measured will have a part called by the same name as the measuring number.
如果一个数被某个数测量，那么被测量的数将有一个与测量数同名的部分。
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For let the number A be measured by any number B; I say that A has a part called by the same name as B.
设数A被数B测量，则A有与B同名的部分。
For, as many times as B measures A, so many units let there be in C.
取C为B测量A的次数，则B通过C中的单位测量A。
Since B measures A according to the units in C, and the unit D also measures the number C according to the units in it, therefore the unit D measures the number C the same number of times as B measures A.
单位D通过C中的单位测量C，因此D测量C的次数等于B测量A的次数。
Therefore, alternately, the unit D measures the number B the same number of times as C measures A; [VII. 15] therefore, whatever part the unit D is of the number B, the same part is C of A also.
由VII.15，D与B的比等于C与A的比，故D是B的多少分之一，C就是A的多少分之一。