In this formula challenge, we have four tests (Test A, Test B, Test C, and Test D), all with the same 19 questions, but listed in a different order. What formula can be used to match questions and construct an answer key for all tests? A perfect use for Excel's powerful lookup formulas.
The challenge - calculate the difference from the current and last entry, even when previous entries are skipped. This is one of those problems that seems simple at first glance, but is tricky when you look closely.