The interviewer says: 'The market is growing at 17% annually from a $340M base. What's the market size in three years?'

You freeze. Not because the math is hard, you could do this on paper in 30 seconds, but because you don't have paper. And fumbling for two minutes while the interviewer watches kills your momentum.

Here's what I learned after doing hundreds of cases: interviewers aren't testing if you can multiply. They're testing if math slows you down. Can you keep thinking about the strategy while also calculating? Or does every number become a five-minute derailment?

Good news: the math in cases is deliberately simple. You won't see calculus or obscure formulas. It's percentages, multiplication, division, middle school stuff. The challenge is doing it quickly and confidently while talking through your reasoning.

This lesson teaches five techniques that cover 95% of case math. Not tricks to memorize, thinking patterns that make numbers easier to work with. After practicing these, you'll handle case math the way consultants do: as a minor step in solving the real problem, not the problem itself.