英语语法分析

Rho is a density, right?

ρ是密度，对吗？

So these two together, l times rho, give us mass per unit area.

这两个量，l乘以ρ,一起给出单位面积上的质量。

The total mass is the volume, which is the area times the length times rho.

总质量是体积，也就是面积乘以长度乘以密度。