I don't really think that you covered all the details of the subject, Demon Duck.
The main problem here is that writing ab/cd isn't following the standard for math notation (at least, as far as I know).
So, when we write ab/cd do we mean:
(a.b)/(c.d), where "." means the multiplication period, i.e.,
Or does ab/cd means:
a.(b/c).d, i.e.,
=a.b.d/c
If we're programming, when we write a*b/c*d (with "*" meaning multiplication), this is equal to a*b*d/c. If I want to have the first case, I'll have to write a*b/(c*d) or a*b/c/d.
By the way, usually the computation of a*b/(c*d) is slightly faster and uses a bit more memory than a*b/c/d.