You have just finished a difficult BCG first-round case. You reached the answer, but setting up the equation took too long and you ran out of time to give a conclusion. Another interview is later today. What should you do before it starts?
Make one small correction, then reset. Write down how you will set up the next calculation, take a short break and enter the second interview ready to solve its problem. You cannot change the first case during the break, and trying to overhaul your preparation now will make the next one harder. The sections below show how to use that interval, make your maths easier to follow and keep a short conclusion ready.
Use the break to reset, not to rebuild your preparation
Write one sentence about the useful lesson: “I need to state the equation and units before calculating.” Then put the case away. Check the next meeting link, get water and give yourself a few minutes without preparation material.
If you have enough time for a warm-up, use a familiar, simple calculation. Do not open a new advanced case or start learning a different framework system. You want to make an existing process available under pressure.
Treat the next interviewer as a new conversation. Listen to their prompt fully. Avoid compensating for the earlier difficulty by speaking faster, asking fewer clarifying questions or rushing into arithmetic.
Make the numerical setup visible
When a problem feels confusing, name the quantity you need. Then explain what information produces it. Write the equation in words before substituting the numbers.
For example, a company is considering a service contract. It expects 15,000 jobs annually, charges £40 per job, spends £25 per job and would incur £180,000 in additional annual fixed costs. The question is whether the contract adds operating profit.
Say: “I'll calculate contribution per job, multiply by annual jobs and subtract the extra annual fixed cost.” Contribution is £15 per job, total contribution is £225,000 and annual profit is £45,000.
Now check the scale. Fifteen thousand jobs earning roughly £15 each should produce a few hundred thousand pounds before fixed costs. That check makes a misplaced zero easier to catch.
Finish with the implication: the contract adds £45,000 under the forecast, before any other incremental costs. You have answered a business question, not merely completed a calculation.
Quick Case Math Drill
A cargo-bike courier has been offered a council contract to move library books between branches, needing a dedicated coordinator and extra bikes.
- Contract volume
- 24,000 deliveries a year
- Per delivery
- £6 fee, £3.50 variable cost
- Coordinator and bike hire
- £4,000 a month
How much annual operating profit would the contract add, in £ thousand?
Recover by correcting the implication too
Suppose you learn that the fixed cost is £20,000 per month rather than £180,000 annually. Convert it to £240,000 per year. The contract now loses £15,000 annually.
A clear recovery would be:
I need to put that cost on the same annual basis. At £240,000 of annual fixed cost, the contract loses £15,000 at forecast volume. I would revise my recommendation and test whether price, volume or cost can change enough to make it attractive.
You have identified the issue, corrected the number and updated the decision. A long apology would use time without improving the answer.
After a mistake, you can still make your reasoning clear, check an assumption and use feedback to improve the answer. Put your attention on those next moves.
Keep a short conclusion ready as you work
If synthesis was squeezed out by time, practise maintaining a running view of the answer. After a major finding, note one sentence: what we now know and what it means for the decision.
For the contract example: “At current terms the contract loses £15,000; break-even requires 16,000 annual jobs at £15 contribution.” That is enough to anchor a short recommendation if the interviewer asks you to conclude immediately.
You can then add the next action: investigate whether demand supports the extra 1,000 jobs or whether terms can be renegotiated. Do not wait until the final minute to decide what the analysis means.
When studying a worked interview, pause after the calculation and explain what the result means for the client. Then compare your transition with the demonstrated answer.
Quick Recommendation Drill
A coach operator is considering a new weekend airport route. Near the end of the case, the interviewer asks you to conclude.
- Passenger forecast
- 10,000 a year, untested
- Contribution
- £8 per passenger
- Extra fixed cost
- £76,000 a year
Which one-sentence conclusion should you give the interviewer?
After the interview day, do one useful review
Once both interviews are over, record what actually happened. Which equation was hard to construct? Did you understand the business relationship? Did you lose a number while speaking? Did you recover when the interviewer supplied guidance?
Choose one repair from that evidence. A conceptual gap needs a worked example; a note-taking problem needs a clearer layout; a missing conclusion needs practice stating the decision first. Keep what worked too. Turning the whole day into a failure will not tell you what to change.
Follow the recruiter's stated response timeline. If it passes, send a concise status enquiry. While you wait, test your chosen repair on a fresh case. The mistake-repair method gives you a way to check whether the correction holds without replaying the first interview indefinitely.
Frequently asked questions
Between interviews on the same day
My first BCG case went badly. What should I do before the next interview?
Write one sentence capturing the useful lesson, such as needing to state the equation and units before calculating. Then put the case away. Check the next meeting link, get some water and take a few minutes away from preparation material. The difficult calculation deserves a repair later, but it should not take over your remaining interview.
Should I cram another case or framework during the break?
No. If you have time for a warm-up, use a familiar, simple calculation. Opening a new advanced case or learning a different framework system just before you need to perform adds unfamiliar material. The goal is to arrive settled and ready to solve the next problem.
Fixing the maths and the conclusion
How do I stop freezing when I can't set up an equation?
Name the quantity you need, explain what information produces it, and write the equation in words before substituting any numbers. Saying 'profit equals jobs times contribution per job, minus fixed costs' aloud makes your logic visible. The interviewer can then follow or correct you before the arithmetic begins.
Can you show a worked example of setting up the equation?
Take a service contract with 15,000 annual jobs, a £40 price per job, £25 cost per job and £180,000 of extra annual fixed costs. Contribution is £15 per job, which gives £225,000 in total. After fixed costs, the contract adds £45,000 of operating profit. Writing it in words first shows which figures you used and why.
What should I do if a number turns out to be on a different time basis?
Convert it to the same basis, then rework the implication as well as the figure. A fixed cost of £20,000 per month becomes £240,000 a year. At forecast volume, the contract now loses £15,000 annually. Say this plainly and revise your recommendation rather than quietly adjusting the arithmetic.
Is it bad to change my recommendation mid-case?
No. Revising openly is what a clear recovery looks like. The article's model answer acknowledges the need to put the cost on an annual basis, states the new loss, revises the recommendation and then names what to test next. Defending an outdated conclusion after the numbers have changed would be the weaker response.
How do I avoid running out of time before my synthesis?
Keep a running view of the answer. After each major finding, note one sentence on what you now know and what it means for the decision. For example: 'At current terms the contract loses £15,000; break-even requires 16,000 annual jobs at £15 contribution.' That line anchors a short recommendation if the interviewer asks you to wrap up.
After the interview day
How should I review a difficult case afterwards?
Set aside a short block and record your own behaviours rather than replaying the whole case. Ask yourself which equation was hard to construct and whether you understood the business relationship. Check whether you lost track of a number while speaking, and whether you recovered when the interviewer offered guidance.
Does every mistake need the same kind of practice?
No, the right fix depends on the cause. A conceptual gap needs explanation and worked examples. A note-taking problem needs a clearer page layout and spoken repetition. A missing conclusion calls for practising a running one-sentence summary. Diagnosing the cause first saves time on drills that would not address what went wrong.
When should I chase BCG for a decision?
Follow the recruiter's stated response timeline, and send a concise status enquiry only if that timeline passes. Reading meaning into every pause or interviewer expression will not get you a reliable answer any sooner. The decision comes from the firm's process, not from signals you noticed during the interview.
What should I practise while waiting for the result?
Do one targeted repair, one fresh case and, if your schedule allows, a follow-up session on your personal stories. The aim is to keep useful momentum, not to punish yourself with endless practice. The fresh case also shows whether your repair holds up on a problem you have not seen before.