If a cube number do not measure a cube number, neither will the side measure the side; and, if the side do not measure the side, neither will the cube measure the cube.
若一个立方数不能量度另一个立方数，则其边也不能量度另一边；反之，若边不能量度另一边，则立方数也不能量度另一立方数。
本页以“立方数不测则边不测”整体图解辅助阅读；点、线、角、圆索引已按命题文字和证明步骤校订，可与证明和问答联动。
正文图形由校订坐标生成；点、线、角、圆可与证明和问答联动。
For let the cube number A not measure the cube number B, and let C be the side of A, and D of B; I say that C will not measure D. For if C measures D, A will also measure B.
设立方数A不能量度立方数B，且C是A的边，D是B的边。
[VIII. 15] But A does not measure B; therefore neither does C measure D.
若C量度D，则根据VIII.15，A也量度B，与假设矛盾，故C不能量度D。
Again, let C not measure D; I say that neither will A measure B.
反之，设C不能量度D。
For, if A measures B, C will also measure D.
若A量度B，则根据VIII.15，C也量度D，与假设矛盾，故A不能量度B。