Casey case math drills that actually transfer

Casey's math questions are short, numerical, and time-boxed. They reward two things: a clean mental setup and arithmetic you don't have to think about. The good news is the surface area is small — five or six recurring patterns cover most of what you'll see.

The six drills

1. Percentage growth and CAGR. Practice converting "grew from 120 to 156" into a percentage in under five seconds. Then practice the inverse — "shrank by 18%, what's the multiplier?" Build the reflex: percentage change = (new − old) / old, full stop.

2. Weighted averages. A segment contributes 70% of revenue at 12% margin; the other 30% at 4%. Blended margin? Drill until you can do it without a notepad. Casey loves segment-mix questions because they punish candidates who default to simple averages.

3. Breakeven volume. Fixed cost / contribution margin per unit. Practice with messy numbers: €4.2M fixed, €7.50 contribution. The trick is comfortable estimation — €4.2M / €7.50 ≈ 560k units, then refine.

4. Funnel conversion. 50,000 visitors, 12% click, 8% of those buy, average order €40. Casey questions chain three or four multiplications. Practice typing them into mental scratch in one pass without losing a zero.

5. Sanity checks. Every answer should pass an order-of-magnitude check. Train yourself to round inputs first ("call it 50k × 10% × 10% × €40") to get a ballpark, then refine. The candidates who skip this are the ones who submit "€1,920,000" when the answer is "€19,200".

6. Reverse-engineering. Casey sometimes gives the answer and asks for an input. If a 12% margin produced €240k profit, revenue is €2M. Practice this until it's automatic.

How to drill

Set a timer. Twenty problems, forty seconds each, six days a week. Track accuracy and average time on a simple spreadsheet. The goal isn't to do harder math — it's to do the same math faster and without a calculator. Most candidates plateau because they keep practicing fresh problems instead of repeating the same drill until the patterns are reflexive.

Pitfalls

• Don't memorize formulas you don't understand. If you can't derive breakeven from first principles, you'll freeze when Casey rephrases the question.
• Skip is a valid move. A 90-second question you can't structure is worth less than two 30-second wins.
• Track which drill type slows you down. The fix is targeted reps, not generic "more practice".

Two weeks of disciplined drilling beats six months of casual exposure.