Hello! I wholeheartedly agree with all the great tips Erica has shared in her answers. Here are a few more I would add:

1. The specific method you use doesn't matter as long as the math is organized - so do what works best for you! When I interviewed, my preferred method usually involved writing out simple equations (e.g. P x Q = Revenue, and then substitute the specific numbers below that), but tables would work equally well. As long as the method is quick to write up, relatively clean, and simple to explain, you should be good to go.

2. That being said, be flexible, and try to adapt your process to the case at hand. In some cases, a table would be the cleanest and most obvious solution, whereas in other cases jotting down some numbers or even sketching a graph could be more appropriate. Experiment with different methods in your case prep to understand what works well for which style of question (or work with a coach to get some useful feedback on this), and always try to use the most straightforward method given the question.

3. Regardless of what method you use, make sure to clearly explain what you are doing to the interviewer. Again, the specific method you use doesn't matter as long as it's clear to the interviewer, but a process that feels like second nature to you after all the case prep you've done might look confusing or unfamiliar to an someone seeing it for the first time, so be sure to take your interviewer through each step of your work. You could do this as a voiceover while you are drawing up your table (or its equivalent), or quickly draw first and then recap what you drew second, but saying something like "Here I have organized the numbers in a table, with XYZ in the first column and ABC in the second column..." could be helpful to make sure the interviewer is following along.

4. To echo Erica's point, if you are someone (like me!) whose natural way of solving math problems is with messy scribbles and sums all over the page, I would recommend keeping that work separate from the "neat" math you present to the interviewer. You could even draw a line on the page (e.g. at the 1/4 page point) to set up a "rough work" section to make sure it doesn't bleed into your other notes.

5. If you are allowed to use your own scrap paper in the interview (which will generally depend on the firm and interview stage), you could bring graph paper to help draw more organized tables and graphs.

(editiert)