Free lesson · 3 of 3 free · Case Ace Learn

Case interview math

The math in a case interview is never hard — it is just asked fast, out loud, while someone watches. This free lesson rebuilds the six formulas that carry almost every case — percent change, the business equation, margin, breakeven, payback and sizing, funnel and mix — each one landing on the page line by line: the terms first, then the worked substitution, then the result, exactly the way you should write it on your page in the room. No algebra background needed; the point is order, not cleverness. Read it signed-out, then warm up your arithmetic on our free mental-maths drill.

Start the free lesson → Warm up on the maths drill →
Chapter: 4 · Exhibits and numbers·Format: interactive, reads like a lesson·Cost: free, no card
A sample of the first worked equation in this lesson, shown as it builds in the lesson.

Worked equation

Percent change, worked

  • Movement$55K → $35K
  • Absolute change$35K − $55K−$20K
  • Percent change−$20K ÷ $55K≈ −36%
  • Materiality−$20K ÷ $55K≈ −36% — roughly a third

Explore phase

Start this lesson →

The formulas, one at a time

One phase, six worked equations: every formula is a step-revealed build — terms, substitution, result — the same order your page should follow in the interview.

Movement

Percent change done honestly: absolute change first, percent second, and the materiality check that stops you charting noise.

The engine

The business equation, margin and breakeven — the three that answer “does this make money?” — each worked on the same gym case.

The lens

Payback and sizing, then funnel and mix — the formulas that turn a hunch (“the discount is costing us”) into a number.

The other free lessons: How a case unfolds → Case interview frameworks →

Free bridge: the mental-maths drill

The lesson teaches the formulas; the site’s free mental-maths drill builds the speed. Case Ace’s Case Math and Guesstimate drills then mark your working step by step — 221 drills across 35 lessons, alongside 46 AI-run cases.

Open the maths drill → Start the free trial →

Free account, saved progress

The first part of the lesson is open to everyone. Create a free account — ten seconds, email or Google/Microsoft — and the whole lesson opens, your spot is saved, and the Case Math drills are one tap away.

Continue reading →