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How to practise with these cases
Cover the answer, say your structure aloud, do the arithmetic on paper and only then compare. The format is described the same way by the firms: Boston Consulting Group (BCG) says a candidate is "presented with a realistic business challenge" (BCG careers, read October 2026), and Bain says a consultant candidate may have "a case interview where you work through a problem" (Bain careers, read October 2026). BCG's list of things to do includes "Think Structurally", "Clarify Assumptions" and "Show Your Thinking", and it adds that a case has no single right answer, so reasoning matters most.
All inputs below are made up, in currency units and not any real currency, and every result was computed in a script.1 A model solution is one reasonable answer, not the only one. The work behind the interview is analytical: the U.S. Bureau of Labor Statistics (BLS) says management analysts "recommend ways to improve an organization's efficiency" (BLS Occupational Outlook Handbook, last modified August 2026). Read the case interview guide first if the format is new, and use the market sizing guide for the estimation cases.
Profitability and cost cases
A retailer's sales stayed at 8.0 million but profit fell from 1.2 to 0.72 million. What do you check first?
Check cost first, because with flat sales only cost or the sales mix can explain the drop. Costs rose from 6.8 to 7.28 million, up 0.48 million or 7.1%, which cut the margin from 15.0% to 9.0% and profit by 40.0%.1 Ask which cost line moved, such as materials, labour or rent, and whether the rise is one-off or permanent before proposing a price rise or a cost programme.
Why it is asked: it shows whether you split profit into parts before guessing. Read the full explanation: case interview guide.
A company plans a product at a price of 12 with a variable cost of 7 and a fixed cost of 450,000 a year. How many units does it need to break even?
Divide the fixed cost by the contribution margin, which is the price minus the variable cost per unit: 450,000 divided by 5 is 90,000 units. Break-even is the volume at which profit is zero.1 If the forecast is only 75,000 units, the loss is 75,000, and breaking even needs a price of 13, a rise of 8.3%. Then ask whether buyers will pay 13 or fixed cost can fall.
Why it is asked: break-even is the most common piece of case math. Read the full explanation: case math drills.
A plant spends 2.0 million a year on energy, and a 1.5 million efficiency system cuts that by 25%. Is it worth it?
The saving is 0.5 million a year, so the payback period, the time to recover the outlay from the savings, is 3.0 years.1 Whether that is good depends on the system's service life, the payback the company requires and the risk that energy prices fall. Recommend it if the system lasts well beyond three years and cash is available, and name the energy-price assumption as the first thing to test.
Why it is asked: it tests whether you turn a saving into a decision. Related: frameworks that still work, which covers how to structure a recommendation, not this calculation.
Revenue is flat at 10 million, but profit fell from 2.5 to 1.9 million. What happened?
A shift in the sales mix can explain it. Product A earns a 40% margin and product B 10%. Moving sales from 5 and 5 million to 3 and 7 million cuts profit from 2.5 to 1.9 million, a fall of 24.0%, and the margin from 25.0% to 19.0%.1 Ask why customers moved to product B, and whether price, promotion or availability of product A caused it.
Why it is asked: it separates a total from what is inside it. Related: case math drills, which covers fast arithmetic habits for case math, not this exact calculation.
Knowing it is half the job. Saying it is the other half.
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Start Free Trial →Market sizing cases
How many pizzas are ordered for delivery each day in a city of 2 million people?
Between 21,900 and 22,900 a day, from two routes. By households: 2 million people at 2.5 a household is 800,000 households, and if 20% order one pizza for delivery in a week that is 160,000 pizzas, or 22,900 a day. By people: 4 delivered pizzas a person a year is 8 million, or 21,900 a day.1 The routes differ by 4.3%, so state the range and the weakest input.
Why it is asked: it checks that you cross-check an estimate. Read the full explanation: market sizing guide.
How many public electric vehicle chargers does a city of 300,000 cars need?
About 320 chargers. If 10% of cars are electric, that is 30,000 vehicles. Each charges twice a week and 30% of charges are public, giving 18,000 public sessions a week. A charger open 12 hours a day and busy half that time serves 56 forty-five-minute sessions a week, so 18,000 divided by 56 is 321.1 Say which input you would test first.
Why it is asked: it tests a capacity estimate built from usage. Read the full explanation: market sizing guide.
How many dentists can a town of 150,000 people support?
About 136. At 1.6 visits a person a year the town makes 240,000 visits. A dentist who sees 8 patients a day for 220 days handles 1,760 visits a year, so demand supports 136 dentists, one for every 1,100 people.1 Check the figure with a second route, such as the share of residents who have dental cover, and name the input you trust least.
Why it is asked: supply capacity against demand is a standard sizing pattern. Read the full explanation: market sizing guide.
How much could an airport shuttle to the city centre earn in a year?
About 6.5 million. Assume 9 million passengers use the airport, 40% are visitors who need transport and 15% of them take the shuttle, which is 540,000 riders. At a fare of 12 the revenue is 6.48 million.1 Check the 15% against the alternatives, such as taxis, trains and rental cars, because the shuttle's share is the number you know least.
Why it is asked: it tests a funnel of shares and a sensible sense check. Read the full explanation: market sizing guide.
Market entry and growth cases
A subscription service wants to enter a country with 4 million target households. What share does it need to break even?
It needs about 0.94% of households, or 37,500 households. Each subscriber pays 120 a year and costs 40 to serve, leaving 80, and fixed cost of 3.0 million divided by 80 gives 37,500.1 A share under 1% looks modest, so the real question is whether the company can win those customers at the planned marketing cost and against local rivals.
Why it is asked: it turns a vague entry decision into a required share. Related: case interview guide, which covers how a case is structured, not this exact calculation.
A grocery delivery company considers a mid-size city. Orders average 45 with a 20% gross margin and cost 6 to deliver, and fixed cost is 270,000 a month. How many orders does it need?
Each order leaves 3, since 20% of 45 is 9 and delivery costs 6. Dividing 270,000 by 3 gives 90,000 orders a month, or 3,000 a day over 30 days.1 Compare that with the city's households and likely adoption. If the need is a large share of households, recommend a smaller launch or a higher order value.
Why it is asked: it tests unit economics before scale. Read the full explanation: case math drills.
A firm can enter a new segment for 2.4 million, with profit of 0.3 million in year one rising by 0.3 million a year. When does it pay back?
Payback comes in 3.5 years. Cumulative profit is 0.3, 0.9, 1.8 and 3.0 million after years one to four, so the 2.4 million is recovered half way through year four.1 The answer rests on the growth path, so recommend a staged entry that tests year-one results before the full investment is committed.
Why it is asked: it checks that you read a payback from a cumulative line. Related: frameworks that still work, which covers how to structure a recommendation, not this calculation.
Pricing cases
A company with a 30% contribution margin raises its price by 5%. How much volume can it lose before profit falls?
About 14.3% of volume, given a 30% contribution margin (price minus variable cost, as a share of price). The break-even loss is the price rise divided by the contribution margin plus the price rise: 5 divided by 35. A thinner margin tolerates more: 33.3% at a 10% contribution margin and 11.1% at 40%. If you are given a profit margin instead, ask for the variable cost first.1 Then judge whether customers would leave that fast, and test it on a small group first.
Why it is asked: it is a quick formula that reveals pricing judgment. Related: case math drills, which covers fast arithmetic habits for case math, not this exact calculation.
Text description of the diagram
- At a 30% contribution margin a 5% price rise breaks even at a 14.3% volume loss.
- At a 10% contribution margin the break-even loss is 33.3%, and at 40% it is 11.1%.
Two customers value software and support differently. Is a bundle better than separate prices?
Here the bundle wins. Customer X values software at 90 and support at 30, and customer Y values them at 50 and 70. The best separate prices, 50 and 70, earn 100 plus 70, or 170, while a bundle at 120 sells to both for 240.1 Bundling works when valuations differ in opposite directions. Check that costs are low and that buyers cannot take only the part they want.
Why it is asked: it tests whether you reason from what customers value. Related: frameworks that still work, which covers how to structure a recommendation, not this calculation.
Should a monthly plan priced at 20 offer an annual plan at 200?
Offer it if enough monthly payers would otherwise leave early. The annual price is a 16.7% discount on 240. If monthly customers leave at 12.5% a month they stay 8 months on average and pay 160, so each one who switches adds 40.1 The plan earns less from those who would have paid all 12 months, so estimate that share before recommending it.
Why it is asked: it checks that you weigh who gains and who loses. Related: case interview guide, which covers how a case is structured, not this exact calculation.
Operations cases
A factory has three stages that make 120, 90 and 150 units an hour. Where do you add capacity to raise output the most?
At the slowest stage, which makes 90 units an hour and sets the output of the whole line. A bottleneck is the step whose capacity limits the whole system, and this stage is it. Adding 20 units there lifts output to 110, a gain of 22.2%, and the 120-unit stage becomes the next limit.1 The same 20 units added to the 150-unit stage would raise output by nothing.
Why it is asked: it tests whether you find the constraint first. Related: frameworks that still work, which covers how to structure a recommendation, not this calculation.
A call centre gets 1,200 calls a day and each takes 6 minutes. How many agents does it need?
About 24. The workload is 1,200 times 6 minutes, or 120 hours a day. With 6 productive hours per agent the floor is 20 agents, with no slack at all. Capping occupancy at 85% leaves slack so queues stay short, giving 23.5, rounded up to 24.1 The cap is a judgment, so check it against the wait the business accepts. If calls bunch, size for the busiest hour, not the daily average.
Why it is asked: it tests the habit of adding slack to a capacity answer. Related: case math drills, which covers fast arithmetic habits for case math, not this exact calculation.
A courier must deliver 480 parcels a day, and a van carries 60 parcels a run and makes two runs a day. How many vans?
Five vans. Each van moves 120 parcels a day, so 480 parcels need exactly 4, but a 10% allowance for peaks and breakdowns raises the load to 528 parcels, or 4.4 vans, rounded up to 5.1 Say what the allowance protects against, and compare the cost of a fifth van with the cost of late parcels.
Why it is asked: it tests rounding and buffers in a simple capacity case. Related: case math drills, which covers fast arithmetic habits for case math, not this exact calculation.
Investment and acquisition cases
A buyer can purchase a company earning 5 million a year for 60 million and expects 4 million of annual cost savings. Is the price justified?
Only if the savings arrive. The price is 12 times earnings. If the target is worth 50 million alone, the premium is 10 million, and 4 million of savings before tax is 3 million after a 25% tax rate, so the premium is recovered in 3.3 years.1 Treat the savings as a range, since they are a forecast, and ask what the target is worth on its own.
Why it is asked: it separates standalone value from the value a buyer adds. Read the full explanation: mergers and acquisitions questions and answers.
A company pays 90 to win a customer who brings 12 of gross profit a month and leaves at 4% a month. Is that sound?
Yes, on these numbers. The cost of winning a customer is the customer acquisition cost (CAC), here 90. A customer who leaves at 4% a month stays 25 months on average, so gross profit is 300, which is 3.3 times the CAC, and the 90 is recovered in 7.5 months.1 Test whether new customers leave at the same rate and whether 7.5 months of cash is affordable.
Why it is asked: it tests customer-level economics. Related: case interview guide, which covers how a case is structured, not this exact calculation.
A machine costs 500,000 and saves 140,000 a year for five years. At a required return of 10%, should the firm buy it?
Yes, narrowly. The savings discounted at 10% are worth 530,710, so the net present value (NPV), the discounted value of the savings minus the cost, is about 30,700, and simple payback is 3.6 years.1 A margin that small is easily erased: if the savings are 10% lower, the NPV falls to minus 22,361. Test the savings estimate and the machine's life first.
Why it is asked: it checks that you compare value across time. Read the full explanation: financial modeling interview questions.
Follow-up questions
How can I prepare for a consulting case study interview?
Learn structure, market sizing and case math, then solve full cases aloud and review each against a model solution. Work from the investment banking interview guide if you also face finance-style questions, and keep your own experience stories ready alongside the cases.
How many practice cases should I solve before a case interview?
No source fixes a number, and firms describe the case as a test of reasoning, not recall (BCG careers, read October 2026). Solve cases until your structure, arithmetic and recommendation are steady, and track which family you drop points on.
How do I check my answer to a practice case?
Compare your structure, your numbers and your recommendation separately. A different structure can still be right, so check that every branch is covered once and that your recommendation follows from your numbers.
- Solve each case aloud first; the model solution is one reasonable answer, not the only one.
- Break-even is fixed cost divided by contribution per unit: 450,000 over 5 gives 90,000 units.
- A 5% price rise at a 30% contribution margin (price minus variable cost, as a share of price) breaks even at a 14.3% volume loss.
- The slowest stage of a line sets output: adding 20 units there lifts 90 to 110, and elsewhere adds nothing.
- Check every estimate a second way, as the pizza routes did within 4.3% of each other, once both counted pizzas.
- A positive net present value can be erased by a small shortfall, so test the input that carries it.
Sources
- Case Interview Preparation — Boston Consulting Group careers site (date = read date), 24 Oct 2026
- Interview process — Boston Consulting Group careers site (date = read date), 24 Oct 2026
- Our Hiring Process — Bain & Company careers site (date = read date), 24 Oct 2026
- Management Analysts, Occupational Outlook Handbook — U.S. Bureau of Labor Statistics (page last modified 2026-08-27), 27 Aug 2026
