Almost every case interview across all consulting industries includes one specific section devoted to evaluating the interviewee’s ability to handle a mathematical problem. Even though it does not include any advanced mathematical equations and it simply relies on basic algebra, this section also tends to be the most dreaded part by applicants without a math background.
This article will cover four best practice tips for successfully navigating any math calculation for consulting interviews, with a specific emphasis on interviews by McKinsey, BCG, and Bain.
1. Structure first, calculations second
Writing out your structure of how you will approach the math problem before you start your calculations has numerous benefits and is guaranteed to make you stand out.
Firstly, it will allow you to receive feedback from your interviewer in case your method of finding the correct answer is incorrect.
Secondly, it shows that you know how to structure your thoughts and have a meticulous approach when it comes to working with data, two attributes that are highly sought after in the consulting world.
Thirdly, in case your final calculation is incorrect it will be much easier to walk through the math with your interviewer and determine exactly where the error occurred. This is especially important if you are having an online interview as the other party will not be able to see your notes.
2. Accuracy beats speed
It’s crucial that you double-check your numbers before reading them out loud.
Many candidates think that completing a calculation faster will impress their interviewers, but accuracy is much more important than speed.
If you focus solely on completing the math part as soon as possible, you might miss out on a few zeros and come up with a number that makes no sense. For example, if you are told to calculate the number of cars sold in the U.S. each year, your chances of making it to the next round will be much higher if you take 2 minutes to determine that it’s ~20 million, rather than if you take 1 minute and say that it’s 200 million.
3. Keep track of zeros using scientific notation
The most common math error I made myself and saw most of my friends make while casing was when multiplying numbers that have a lot of zeros e.g., multiplying 15 million by 10 thousand.
Similar to other aspects of the case interview, practice makes perfect. But if you are specifically struggling with zeros, a great ‘hack’ is to write all numbers in scientific notation. It will take a couple of cases to adjust to this format, but I found it greatly increases the speed and accuracy of calculations that involve a lot of zeros.
4. Errors are not the end of the world
Based on my conversations with MBB interviewers, the most common pitfall when it comes to the math part is not knowing how to deal with an error.
Interviewees often think that because they miscalculated or missed a zero that their application is ruined, and their performance in the case will diminish after that. However, this couldn’t be further from the truth. Most interviewers are more interested in your approach and way of thinking rather than your ability to multiply numbers. Moreover, realizing that you made an error and then handling the situation well will work in your favor as it shows your ability to deal with problems in a high-stress environment.
The bottom line
The math part isn’t nearly as intimidating as people perceive it to be initially. Most often the interviewer is much more interested in examining your approach rather than basic algebra capabilities. Make sure to prioritize accuracy over speed, practice calculating percentages to impress your interviewer, and remember that a simple error does not mean the end of your candidacy; it is a great opportunity to further showcase your skills.
Drin Krasniqi is a junior student at Harvard studying Economics and Computer Science. He is a member of one of the most prestigious student groups at Harvard, Consulting on Business & the Environment, where he has worked for businesses worth over $120 billion.
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