We’ve saved the best for last in this 3-part guide to doing mental math in interviews: the vaunted market sizing question. (Part 1 was on basic tips and frameworks, and part 2 was on calculating growth rates).

While every consulting recruiting process is a little different, market sizing questions are one of the incontrovertible truths—they always come up! Again, this makes perfect sense too because the McKinsey, BCG and Bains of the world are continually hired to help companies size opportunities, launch new markets and new product lines. Clearly, market sizing is a critical part of all those exercises. Let’s look at a sample problem.

To check out the sample problem: How to Solve Market Sizing Questions: Consulting Interview Skills