All,
I conferred with Kevin Reilly and he has the following advice:
Based on my personal experience in PMP Exam Prep, as well as my conversations with students who have taken the exam, I have never run across the need for the exam taker to “calculate” depreciation. Having said that, I do believe it is important for the exam taker to understand the difference between Standard Depreciation (AKA Straight Line Depreciation) method and Accelerated Depreciation methods, such as Sum of the Year’s Digits and Double-Declining Balance.
So my recommendation would be that you absolutely need to know the general concepts, you should understand how the formula works and maybe even invest an hour or two in answering a few sample questions and applying the formulas. But then move on to those formulas that you will for sure encounter on the exam. And that's Earned Value.