Are there times you must either add or multiply inflation? e.g. 3% real return with 2% inflation = 5% if you add, or (1.03)(1.02) - 1 = 5.06%. Old CFA answers seem to say either is OK, but then I saw in Schweser practice test Vol 2 Exam 3 Question 11 that if the goal is perpetual you have to multiply instead of add? Can’t find that in the notes though. Can you ever go wrong with multiplying (it’s not like it’s so much harder than adding)?
No, you can never go wrong multiplying.
I simply always go with addition because it’s quickest and easiest. Have yet to see any CFA guideline not give full credit for simple addition
You will always be safe if you multiply in the CFA exam
However the CFAI curriculum explains that you use addition for short term periods eg one year or two years, and use multiplication for longer term periods (because multiplication factors in compounding so is more accurate esp for longer periods)