3) Structured Analysis
You're on a new project involving real estate, something you haven't done before. you'd like to get it done quickly, because your friend has a moving-away party tonight.
You're opening one excel sheet after another, alt-tabbing between 3 different countries' local data as you prepare scenarios. It's a lot to keep track of, but the calculations are little more than basic arithmetic.
Approach A: You continue as you have, straight copying and pasting data (hard-coding) and not labeling or formatting anything since you just need a final number. You've got it all in your head. You finally get the number you need and email it to your manager.
He comes back after his meeting and asks you exactly HOW you came up with that calculation, saying that the client wants to see a full backup. In case you're not sure, this is because the figures look very wrong.