Profitability cases are the single most common thing you will meet in a consulting interview, and they all start from one small equation: profit is what a business keeps after paying for everything it needed to earn that money. This deck builds from there, assuming you have never opened a financial statement and would rather not pretend otherwise. You will learn to split a profit decline into revenue and cost, narrow it down to a product, a region or a customer segment, and put real numbers behind ideas like contribution margin, break-even and mix. By the end, a client saying profits are down twelve percent should feel like the opening of a conversation rather than a trap.
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Card 1 of 18
Before anything else: what is profit, and why is a company with enormous revenue not automatically a profitable one?
Profit is what is left of revenue once every cost of running the business is paid.
Revenue is all the money customers hand over during a period, usually a year. Costs are everything the business spends to earn that money, so materials, wages, rent, marketing, interest and tax. Profit is simply revenue minus costs, which means a company can sell a billion dollars of product and still lose money if it spent more than a billion getting there. That subtraction is the whole game, and it is why an interviewer who says profits are down is never really asking about sales, but about which side of it moved.
Card 2 of 18
Your interviewer says Calder Foods lost 12% of its profit last year and asks how you would break the problem apart. What does the profit equation look like drawn as a tree?
Profit = (price x quantity) - (fixed + variable costs), and every driver hangs off one of those four boxes.
Revenue is price times quantity: what you charge per unit and how many units you sell. Costs split into fixed costs, which do not move with volume, such as rent and salaried staff, and variable costs, which rise with every extra unit, such as ingredients and packaging. So profit equals price times quantity, minus fixed plus variable costs, and any explanation for Calder’s 12% drop has to land in one of those four boxes. Drawing that tree out loud early gives you a map, and it shows the interviewer where you intend to look first.
Card 3 of 18
What is a profit margin, and how can a company’s profit go up in a year when its margin goes down?
Margin is profit as a percentage of revenue, so it can fall even while total profit rises.
Margin is profit divided by revenue, written as a percentage: earn 8 million of profit on 100 million of revenue and the margin is 8%. It answers a different question from absolute profit, which is the raw dollar amount, because margin tells you how much of every sales dollar the business actually keeps. If revenue doubles to 200 million while profit reaches 12 million, profit is up but the margin is now 6%, so each dollar of sales is worth less than before. Always ask which one the client cares about, because a growth story and a margin story lead to different recommendations.
Card 4 of 18
A partner drops you into a case with one line: Northbay Logistics says profits are down and wants help. What do you establish before you touch a single number?
Pin down how much, over what period, measured against what, and what the client actually wants to achieve.
Profits are down is a symptom, not a question. Ask how large the decline is, since 2% and 30% call for very different responses, and over what period, since one weak quarter and a five-year slide are different problems. Ask what the comparison is: down against last year, against budget, or against competitors. Then ask what success would look like, because a client that wants last year’s profit back within twelve months needs different advice from one willing to spend three years rebuilding. Interviewers leave this deliberately vague to see whether you scope a problem before you start solving it.
Card 5 of 18
How do you work out whether a profit decline is a revenue problem or a cost problem, and what is the first data you ask for?
Ask for revenue and total cost separately over the same years and see which line actually moved.
Since profit is revenue minus cost, only three things can have happened: revenue fell, cost rose, or both. So ask for both lines over the same several years and look at which one moved and by how much. If revenue held flat at 400 million while total cost climbed from 360 to 390, you have a cost problem, and the rest of the case belongs on the cost branch of your tree. Making this split early is what stops you spending fifteen minutes exploring pricing in a case that was always about warehouse expense.
Card 6 of 18
You have established that Ferrow Retail’s revenue fell from 500 million to 450 million. Your interviewer asks whether that is a price story or a volume story. How do you separate the two?
Hold one lever still at a time to see how much of the drop came from price and how much from volume.
Revenue is price times quantity, so a 50 million shortfall has to come from a lower average price, fewer units, or some blend of both. Ask for units sold and average price in each year. If Ferrow sold 10 million units at 50 dollars and now sells 10 million at 45, the entire decline is price. If price held at 50 and units fell to 9 million, it is entirely volume. When both move, value one effect at a time, the volume effect at the old price and then the price effect on the new volume, so the two pieces add back to 50.
Card 7 of 18
Northbay’s total cost line looks unremarkable, and then the interviewer slides over a table of profit by region. What are you looking for, and how do you decide where to dig?
Averages hide problems, so cut profit by product, region, customer and channel until one piece stands out.
A company total is an average of many smaller businesses, and averages hide things. So cut the profit number every way the data allows: by product line, by region, by customer segment, by sales channel and by time period. Usually one slice is dragging the total down while the rest is perfectly healthy, and that changes the answer entirely, since repairing one bad region is a very different project from fixing a company-wide margin. Name the cuts you want before the data appears, so the interviewer sees that you went looking for the outlier rather than stumbling onto it.
Card 8 of 18
You have found where the profit is leaking. How do you tell whether the cause is something the client did to itself or something the whole industry is living through?
Check whether competitors show the same pattern, because an industry-wide problem needs a different answer.
Ask whether rivals in the same market are seeing the same squeeze. If every regional grocer’s food cost jumped in the same year, the cause is external, an input price shock or a shift in demand, and the useful question becomes how the client responds faster than its peers rather than what it did wrong. If the client alone is deteriorating while competitors hold steady, the cause is internal, and you look hard at its own pricing, contracts and operations. Recommending an internal fix for an industry-wide problem is one of the most common ways candidates get a case backwards.
Card 9 of 18
What is contribution margin, and what does it tell you that the headline profit number does not?
Contribution margin is what one extra sale leaves behind after its own variable cost, before any fixed costs.
Take a single unit. Calder Foods sells a jar of sauce for 6.00 and spends 2.20 on the ingredients, packaging and line labour for that jar. The 3.80 left over is the contribution margin: the amount that jar contributes toward covering fixed costs such as the factory lease, and toward profit once those costs are covered. It matters because headline profit folds fixed and variable costs together, while contribution tells you what one more sale is genuinely worth. That is the number behind almost every decision about volume, pricing, or whether a product deserves to stay.
Card 10 of 18
Calder Foods is weighing up a new sauce line, and the plant it would need costs 1.9 million a year to run whether it makes one jar or a million. How do you find the break-even volume?
Break-even quantity is fixed costs divided by the contribution margin on one unit.
Break-even is the sales volume at which profit is exactly zero, the point where the contribution from every jar sold has just finished paying off the fixed costs. Each jar contributes 3.80 and fixed costs are 1.9 million, so you need 1.9 million divided by 3.80, which is 500,000 jars, before Calder earns a cent. Every jar after that adds 3.80 straight to profit. The calculation earns its keep in an interview because it turns a vague question, is this worth doing, into one the client can actually judge: can we realistically sell more than 500,000 jars a year?
Card 11 of 18
Two rivals each lose 10% of their volume in the same year. One owns a large factory, the other pays an outside supplier to make everything. Why does the identical volume drop hurt one far more?
High fixed costs do not shrink when volume falls, so every lost unit takes its full contribution with it.
Variable costs fall automatically when you make less, so the outsourcer’s costs drop roughly in step with its sales and its margin barely moves. The factory owner still pays the same lease, depreciation and salaried crew whether the line runs full or half empty, so those fixed costs now spread across fewer units and the cost per unit climbs. That sensitivity is called operating leverage: heavy fixed costs magnify profit in good years and magnify losses in bad ones. It is why a case about a manufacturer, an airline or a hotel chain usually turns into a question about volume and how full the capacity is.
Card 12 of 18
Bramwell & Co sold the same number of units this year as last, and has not cut a single price, yet profit fell 9%. What is the most likely explanation?
The mix shifted, so customers bought more of the low-margin products and fewer of the high-margin ones.
Mix is the split of your sales across products that carry different margins, and it moves profit even when price and volume look untouched. If Bramwell sells a premium line contributing 40 per unit and a budget line contributing 10, and the split slides from half and half to 30/70, average contribution falls from 25 to 19 without a single price change. You find it by comparing contribution by product across the two periods rather than staring at total units. Interviewers like this one because candidates who check only price and volume tend to declare the case impossible.
Card 13 of 18
Ferrow Retail launched a cheaper own-brand cereal that sold 400,000 boxes in year one, and total profit in the cereal aisle still went down. What happened?
Sales that come out of your own existing products are cannibalised, not incremental.
Cannibalisation is when a new product’s sales are taken from the company’s other products rather than from competitors or from genuinely new demand. If 300,000 of those boxes went to shoppers who would otherwise have bought Ferrow’s higher-margin branded cereal, the company traded high-contribution sales for low-contribution ones, and only 100,000 boxes were truly new. The test is always incremental contribution: total contribution with the launch, against what it would have been without it. Any new product, price cut or extra store deserves that check before anyone calls the volume number a success.
Card 14 of 18
Your team wants to know whether Northbay’s warehousing cost is genuinely too high. How do you benchmark a single cost line against competitors, and why convert everything to a per-unit basis first?
Compare cost per unit against peers to find the line that is out of step rather than merely large.
Benchmarking means setting the client’s cost beside what comparable companies spend on the same thing. Raw totals are useless for that, because a rival twice the size spends twice as much on almost everything, so first convert to a common basis: cost per unit shipped, per store, per employee, or as a share of revenue. If Northbay spends 14% of revenue on warehousing while peers spend 9%, you have isolated a real gap worth roughly five points of margin. Then ask why, since the gap may be a deliberate choice, faster delivery for example, rather than waste to be stripped out.
Card 15 of 18
Ferrow Retail’s CFO wants 15% taken out of every cost line by year end and asks you to bless the plan. What is your concern?
Some costs buy future revenue, so a blanket cut can lift this year’s profit and shrink next year’s.
An across-the-board cut treats every cost as equally wasteful, and they are not. Renegotiating rent or removing duplicated back-office work takes cost out without a customer ever noticing. Cutting store staff, maintenance, product quality or marketing lowers cost immediately but erodes the revenue line over the following year or two, so profit improves briefly and then falls below where it started. The honest answer separates costs that buy future revenue from costs that simply exist, and tells the client plainly which lever they are pulling, because a one-year margin win that costs three years of growth is not a win.
Card 16 of 18
One of Northbay’s twelve depots reports a 200,000 loss once its share of head-office cost is charged against it. Should the client close it?
Close it only if its own revenue fails to cover the costs that would genuinely disappear on closure.
A reported loss usually includes allocated overhead, a slice of head-office and central cost pushed onto each site whether or not closing that site removes any of it. Suppose the depot brings in 1.4 million, spends 1.3 million on costs that really would vanish on closure, and carries 300,000 of allocated overhead. It is contributing 100,000 toward central costs that the other eleven depots would otherwise have to absorb, so closing it makes the company worse off, not better. Ask for contribution before overhead allocation, and ask exactly which costs go away.
Card 17 of 18
The interviewer adds that Northbay spent 4 million fitting out that same depot two years ago, and the CEO keeps mentioning the figure. How should it affect the decision to close?
It should not, because money already spent and unrecoverable belongs nowhere in a forward-looking decision.
A sunk cost is money already spent that you cannot recover no matter what you choose next. The 4 million is gone whether the depot stays open or shuts tomorrow, so it cannot change which option leaves Northbay better off from today onward. The only figures that belong in the decision are future ones: the contribution the depot will earn if it keeps running, set against closure costs and whatever the site would fetch if sold. People resist this because walking away from a large investment feels like admitting a mistake, and that bias is exactly what the interviewer is testing by mentioning the number at all.
Card 18 of 18
Calder Foods’ profit fell from 40 million to 28 million. Revenue is flat, units are flat, no price changed, and no single cost line looks unusual. Walk me through how you would hunt down the missing 12 million.
When price, volume and totals all look flat, the answer is nearly always hiding in mix or in one segment.
Start by checking that the flat totals are really flat rather than two offsetting moves, since a growing premium line and a collapsing budget line can net to zero. Then cut the business apart, contribution by product, region, channel and customer size, hunting for the slice that shifted. Test mix explicitly, because steady units at a worse blend of products drags contribution down without disturbing any headline number. If every cut looks clean, ask whether volume was held by heavier discounting, or whether fixed costs are now spread over fewer production runs. Finally benchmark against peers to see whether the cause sits inside Calder or across the industry.
Reading is not the same as remembering. Study this deck with scheduled review so the cards come back before you forget them.