Have you ever finished a GMAT problem, read the explanation (or listened to your instructor give it), and thought “well how was I supposed to know ___________?!”?
If so, you’re not alone. Many test-takers become frustrated when the key to a tricky question falls outside the normal realm of math. How was I supposed to know to estimate? How was I supposed to know to flip the diagram over to notice that side AB could also be the base of this triangle? How was I supposed to know that the word “production” next to “costs” was going to be so important?