Many commenters have already said it: the article is probably not helpful when teaching kids. Or is it? I recall having asked myself these questions at school:

Many commenters have already said it: the article is probably not helpful when teaching kids. Or is it? I recall having asked myself these questions at school: if lines are infinitely thin, how is it repeated addition that defines surface areas? What is "inside" the variables we use as units? Measure theory (for your volume) and the structure of dimensional quantities [1] are non-trivial topics, and while probably not giving good answers, I think the article is certainly asking good questions. [1] https://terrytao.wordpress.com/2012/12/29/a-mathematical-formalisation-of-dimensional-analysis https://terrytao.wordpress.com/2012/12/29/a-mathematical-for...