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Advice / Job Search / Interviewing

Secrets for Cracking the Quant Interview

Thinking about management consulting? This week, we’re bringing you a consulting mini-series to help you decide if the field is right for you, ace your case, and tackle the quant interview.

You’ve aced the practice case, nailed the recruiting meet-and-greet, and you’re ready for consulting stardom. Now there’s just one thing between you and glory: the quantitative analysis.

Most likely, if quant is going to come up during your interview, it will make its appearance in the midst of a case interview. The first step in the case was to figure out that the key to growth is building a new factory, or the biggest savings lever is to cut down some variable costs. Your interviewer nods approving—and asks, “So, what numbers are we expecting here?” And now, it’s time to actually roll up your sleeves, work out those numbers, and tell your interviewer what percent annual growth or how many millions of dollars in savings your strategy is expected to reach.

Yes, doing math while someone sits across the table from you watching can be a bit daunting. So how to crack the quant? Here are the tips that current consultants and interviewers recommend.

1. Slow Down and Breathe

It can be really easy to let adrenaline take over in a big interview, setting your pulse racing and sending jitters up and down your spine. But remember, it’s OK to take a moment to calm down and think through the problem. Taking a deep breath and saying, “This is really interesting. Let me take a moment to think about this,” is a great way to buy yourself some time. Letting the interviewer know you need a few seconds to step back and think before you get started also shows you aren't just jumping into the problem—plus it gives you time to organize your thoughts.

2. Talk it Through to Get Credit Where You Can

No matter how comfortable you are doing mental gymnastics, impromptu number-crunching while being scrutinized by an interviewer can trip anyone up. One way to make sure that one little mistake doesn’t cost you big is to talk through your calculations with the interviewer. Showing him or her that you understand which inputs you need and what calculation needs to be made allows your interviewer to give you credit for your answer, even if the final number is off.

For example, let’s say your interviewer asks you how much money you would expect to make off of building that new factory you suggested. First, you might say, “Well, our revenue will be determined by how many widgets [shoes, cars, golf carts—whatever] the factory can produce, and then we’d subtract our costs to find out our profits.” You’ve already earned some credit: You’ve shown you understand how the company makes money (by selling widgets), and that you understand the difference between revenue and profits.

Now, you continue: “Let’s assume we build a factory the same size as our current one. You mentioned before that we currently make 1.5 million widgets a year—so if I divide that by approximately 50 weeks in a year, that will tell me how many widgets a factory can make in a week.” And then, you pull out your paper and do the division. This is where it’s easy to get tripped up—does 1.5 million divided by 50 come out to 3,000 or 30,000? Yes, it’s best to get to the right answer (and messing up zeros is the most common mistake, so watch out for it)—but if you explain what you’re doing to your interviewer and propose the right calculation, he or she is a whole lot more like to give you a break if you do miss a zero.

3. Engage Directly With the Interviewer

If you need a piece of information—say, the number of employees, or the last year’s sales—ask for it. And as you’re working, if your interviewer isn’t particularly responsive, look up at him or her. With most people, you should be able to tell right away if he or she thinks you’re on the wrong track. (Hint: nodding and smiling is a good sign; furrowed brow, bad.)

A good interviewer will even correct you if you veer off the path—but again, only if you’re allowing him or her to see your thought process. Why? Because your interviewer isn’t just trying to test your math—the goal of the interview is to see what sort of a teammate or employee you would be, and how you respond to being corrected and guided back to the right answer will tell your interviewer as much (or more) about you as your division skills will.

4. Use Common Sense

If you make a mistake during a quant problem, it isn't the end of the world. But making a mistake that clearly gives an unrealistic answer—and not catching it—is much worse. So before giving an answer, take a second to think about whether your response actually makes sense. For example, if your one new factory can increase the company’s production 20 times, or the average cost per good goes from 37 cents to 2 cents after reducing labor costs by 10%—you probably missed something, somewhere. Use your head, and you’ll catch a lot.

If you do realize you’ve made an error, just tell your interviewer, "Wait, 2 cents per widget can't be right, let me double check that." You’ll end up impressing him or her with your composure and your ability to check your own work. And hey, you may even make more of an impact than if you had gotten it right in the first place—now your potential employer knows that you would do a quality check before sending your work to a client or a senior manager.

5. If You Make a Mistake, Keep Your Cool

Mistakes happen. Plenty of people make them, and they often get the job despite them. The problem comes when you let the mistake get to you, and you become less composed, which can have more of an impact on your interview than the actual mistake. So just breathe, take a second, and move on. You can't do anything to take the mistake back, but you can wow your interviewer for the rest of the day.

Doing math under observation is nobody’s favorite part of the interview—but stay calm, thoughtful, and engaged, and you’ll be able to turn the quant section into an opportunity to showcase the way you think and your ability to get to a concrete answer. And no matter what happens, don’t get flustered—there’s a whole lot more to your future job than long division, and you can impress the person across the table even if you make a mistake.

Photo of woman taking notes courtesy of Shutterstock.