A dialogue where students discuss multiplication.

Check out this dialogue between two calculus students (based on a true story):
Devyn
Hey Riley, I was reading about the history of mathematics.
Riley
Really? Tell me about it!
Devyn
Apparently, back in the day, mathematicians worried about writing things like:
Riley
Why? What’s the matter here?
Devyn
Well, they thought of as an area. But was thought of as a length. Apparently they worried whether it made sense to add ‘‘areas’’ and ‘‘lengths.’’
Riley
Hmmm. We don’t seem to worry about that now. I wonder why?
What are some ways to interpret ?
Answer will vary.