How to crack a profitability case (in plain English)

"Our client's profits fell 20% last year. Why?"

If you're preparing for consulting interviews, you will hear some version of this question. It's the most common case type — and the one people overcomplicate most.

Here's the simple way to think about it.

Step 1: Ask one question before anything else

Every profit question starts with one line:

Profit = Revenue − Cost

So profit can only fall for two reasons: less money came in, or more money went out. Before you draw any framework, say out loud:

"I'd first like to understand whether this drop is revenue-led or cost-led."

That single sentence tells the interviewer you're structured — and it cuts the case in half.

Step 2: Split revenue into price and volume

Revenue = Price × Volume

If revenue fell, either the company sold fewer units (volume) or got less per unit (price). Then split further by segment, product, channel or region to find where it moved.

• Did one product line collapse?
• Did discounts quietly grow?
• Did a big customer leave?

Step 3: Split cost into fixed and variable

• Fixed costs don't change with sales: rent, salaries, software.
• Variable costs grow with each sale: raw materials, packaging, delivery, commissions.

Ask which line grew fastest. A spike in variable cost per unit tells a very different story from a jump in rent.

Step 4: Check the outside world

Before concluding, ask: is the whole industry suffering, or just this company? If competitors are fine, the problem is internal. If everyone is struggling (input prices, regulation, demand), your recommendation changes.

A worked example

A café chain's profits fell 20%. Customer numbers are flat.

1. Revenue: customers flat, but the average bill rose 5% after a menu refresh → revenue grew.
2. So it's cost-led. Split costs: rent and salaries flat; variable costs jumped.
3. Driver: delivery orders went from 10% to 35% of sales, and delivery apps take ~25% commission.
4. Answer: the shift to high-commission delivery explains most of the drop.

Recommendation: push direct ordering, price delivery menus higher, protect dine-in. Risk: some delivery volume may fall.

The mistakes that cost people offers

• Dumping a framework without linking it to the client's situation.
• Never stating a hypothesis. Say your best guess early and test it.
• Ending without a recommendation. Always finish answer-first: what should they do, why, and what's the risk.

Practise it

Reading this helps. Saying it out loud under pressure is what actually builds the skill. Case Flex gives you an AI interviewer that runs profitability cases like this one, pushes back, and scores your structuring, quant and synthesis.