Quickest way to do n/(n+m) on a 4-function calculator

Question

Let's say the problem I want to solve is:

I have n "widgets" and m "doodads". I want to know what percentage of the total items are widgets.

Let's say I only have a basic 4-function calculator (+-*/) (maybe or maybe not having memory buttons, i.e. M+, M-, MR).

Questions:

1. Is there any way to do this in a single calculation? (I don't think so)
2. If not, what is the easiest (i.e. fewest number of keystrokes) way to do this?
3. Can it be done without having to write down or remember an intermediate value?
4. Can I do #3 it without having to enter either of the numbers (n or m) more than once?

My best solutions so far using memory buttons:

#3: n + m = M+ C n / MR =

#4: n M+ + m = / MR = MC M+ C 1 / MR =

They're both kind of a lot of keystrokes. Any better ideas?