Practice · Case Math
Every case is a math case.
Pick a case type for its full formula sheet, then solve the calculation waterfalls line by line — type each answer, check it, and watch the exhibit build to the business result. Suffixes like k, M, % are fine (e.g. $5.7M, 82k, 12.5%).
Formula Sheet · Profitability
Everything hangs off Profit = Revenue − Cost. Decompose each side, benchmark how fast each line grew, and quantify the outlier with a counterfactual.
Profit
Profit = Revenue − Cost
Revenue
Revenue = Price × Volume
Volume
Volume = Customers × Frequency × Units per visit
Split volume before analyzing — flat revenue can hide offsetting moves.
Cost
Cost = Fixed + Variable
Contribution margin
CM = Price − Variable cost (per unit)
What each unit contributes to fixed cost and profit.
CM %
CM% = (Price − Variable cost) ÷ Price
Break-even volume
BE units = Fixed cost ÷ CM per unit
Operating margin
Op margin = Operating profit ÷ Revenue
Counterfactual
Normal = Prior × (1 + benchmark); Anomaly = Actual − Normal
Isolates how much of a change is 'abnormal' vs. expected.
% change
%Δ = (New − Old) ÷ Old
Worked waterfalls
See the frameworkRoast & Grind — Isolating the Labor Anomaly
Starter From: The Declining Coffee ChainRoast & Grind's operating profit fell $4.2M even though revenue was flat. Labor cost rose from $12.4M to $16.1M last year after a minimum-wage change; normal wage inflation runs ~5%.
Goal: How much of the profit decline is explained by labor growing faster than inflation?
$12.4M × 1.05 =