Let’s face it. A major portion of the consulting case interview tests your quantitative skills. Why? Consultants work with a lot of data and can spend a significant amount of time crunching numbers. So your interviewers want to know that you’re comfortable with math and have strong analytic reasoning skills.
Here is a play-by-play of how you should approach a case interview:
1. Talk through your problem-solving approach
When you first uncover or are asked to calculate a math problem, take 5 seconds to figure out how you’ll solve the problem. Then, you’ll need to explain what you’ll do before you do it.
I know what you might be thinking. Why would anyone talk through a math calculation? The simple answer is that this is the way your interviewer will follow what you’re doing, and can question you or coach you along if you happen to go down the wrong path.
If you simply have your head down and arrive at a solution that’s incorrect, the interviewer will have a hard time guiding you to the right answer, because you haven’t articulated your approach beforehand.
2. Use structure
You want to stay organized and structure your math by writing out the equation first, and then solving the problem.
There might be some cases, particularly in the second round, when you’ll have to do multiple calculations sequentially. If you’re not organized, you might end up confusing not just yourself, but your interviewer as well.
Your interviewer should be able to follow along easily. Don’t make it harder for them by being messy or disorganized. Your pieces of paper should act as slides, and while it’s no beauty contest, write in legible, large font.
3. Do calculations on scratch paper
It’s optimal to do mental math, but if you need to do some calculations by hand, use a separate sheet of paper. Again, your main piece of paper should act as a slide. There is a good chance that your interviewer might hang onto your slides to review in order to help him/her decide whether you’re moving on to the next round, getting an offer, or getting the axe. So keep your main piece of paper neat and use separate scratch paper for your calculations.
4. Don’t ask your interview if you have the correct answer
Something I’ve seen in giving mock interviews is that interviewees have a tendency to want to check their answer with the interviewer. I get it – you want to know if you’ve gotten the right answer. But would you ask a real-life client if you’ve gotten the right answer to a problem they’ve hired you for? Instead, state your answer with confidence because you’ve done the math and have the answer.
5. Do a quick sanity check on the final answer
Before you state your answer, just take a quick second to make sure your answer makes sense. For example, if the interviewer asked you to calculate the annual revenue for Apple and you’re final figure is $4 million, then you know you’re off by several orders of magnitude. So make sure your answer makes sense for the problem you’ve been given.
6. Don’t lose zeros
As silly as this sounds, it’s a very common mistake. Being neat helps. But also consider using scientific notation or shorthand for thousands, millions and billions.
7. Answer the interview’s unstated question, “so what?”
Finally, the point of getting to the solution in a math problem isn’t to simply come up with the final number. It’s to come up with the “so what” insight that the final number supports. Analyze the results, so that you can move forward and conclude the case.
Key Takeaway: Whatever you do, never keep your head down and silently do the math. This is one of the unique qualities of the case interview, so it’s worth mentioning again. It’ll take practice, and requires getting over the feeling of awkwardly talking through a math problem. But it’ll all be worth it when you get that second round interview and consulting offer!
Min Kim is currently an MBA student at NYU Stern School of Business where she is specializing in Product Management, Business Analytics and Finance.
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