The interviewer hands you a business problem and watches how you think it through out loud. There's no hidden "correct" answer. It's testing structure and logic, not trivia.
The case types below are consistent everywhere, but the flavour isn't. Worth knowing before you assume one firm's prep is enough for all of them.
Rigorous and fast-paced. Strong mental maths expected as standard, not a bonus. One of the three (McKinsey) runs candidate-led, the other two more interviewer-led. See the interviewer-led vs. candidate-led breakdown.
Leans more into organisational and operational questions alongside pure strategy: how a business actually runs, not just what it should do.
Strategy-first. In practice, a lot of the real project work behind these cases skews toward due diligence and vendor due diligence (VDD): assessing a target company for a buyer, fast.
Alongside whichever type you're in, most cases also lean on two skills that deserve their own practice time.
Fast, accurate mental arithmetic under pressure: percentages, big-number multiplication, sanity-checking a result before you say it out loud. This shows up in every single case type, not just market sizing.
Reading a chart or table and pulling out the "so what," not just describing what's on the page. Comes up most in data-heavy cases, but the skill generalises everywhere.
Nearly every case falls into one of these. Spotting which one you're in early saves you time structuring.
Revenue's down or costs are up. Find out why, then fix it.
Full breakdown with a worked example →
Should we enter this market, country, or segment, and if so, how?
Full breakdown with a worked example →
Estimate how big something is, built up from scratch, no data given.
Full breakdown with a worked example →
Should we acquire this company, and does the price make sense?
Full breakdown with a worked example →
None of this is about knowing more frameworks. It's about how you come across while you work through the problem.
Even a rough framework stated out loud beats diving straight into detail. Structure first, always.
Interviewers can't follow logic they can't hear. Narrate your thinking, even the messy parts.
They're not there to trip you up. They're steering you. A hint you brush past is a point you lose.
Any one of these on its own is usually recoverable. Doing two at the same time is normally the actual line between a pass and a fail.