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Can't wrap my head around the math's logic?

I will have my case study interview with McKinsey soon. I'm doing ok with most things in case studies, my calculations are also correct. The only problem is that I'm really slow, (and sometimes can't even) figure out how to I approach the mathematical questions and what number to use for what.

Is there a way to improve this?

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Top answer
Allen
Coach
on Feb 07, 2022
Ex-McK Experienced Hire and EM - I show you how to perform at your best

Hi There,

Tough question!

When I coach people with this problem, the approach I take is starting at the end and working backwards, not starting at the beginning and moving forward.

For example:

  1. What are you trying to find out
  2. What mathematical formula or equation will allow me to find that out
  3. What information do you need
  4. What information do you already have

I find that many people who struggle, struggle because they get nervous and move too quickly through #1 and #2 and instead jump quickly to #4, hoping to find some clue from the information they already have to figure out what they are solving for (what I call starting at the beginning and moving forward).  Of course, it almost never works that way, and therefore they fail.

Therefore, take your time when you are practicing, don't move forward until you can confidently answer #1.

One more point: often the interviewer is happy to provide additional information as long as you ask the right questions.  Of course, you don't know what to ask (#3) until you've figured out #1 and #2.  Again, take your time and you'll get much better at this.

Happy to help more, just message me.

Hope this helps,

Allen

Moritz
Coach
on Feb 07, 2022
ex-McKinsey EM & Interviewer | 7/8 offer rate for 4+ sessions | High impact sessions + FREE materials & exercises

Considering the shortened time frame, you need quality practice ideally with professional coaches to get to the bottom of the problem and devise strategies to improve quickly.

As you pointed out, arithmetic is not the issue, which is good! However, you do need to learn how to quickly identify when to do math, defining the objective, setting up your equation, do all the computations, synthesize the “so what”, and talk your interviewer through the process as you're doing it.

For most people, this is a tall order and can only achieved through practice. This hardly comes natural to anyone!

As a former McKinsey case coach and interviewer, I can help you with this. Let me know!

Lucie
Coach
edited on Feb 08, 2022
10+yrs recruiting & BCG Project leader

Hi there,

from my own experience and experience from my coachees, it is just drill that can make a miracles. 

I don't drill math, but now after 2,5 years with BCG I am much faster than all my coachees, it is normal to not be fast, but the good thing is you can speed up significantly and focus the energy on what really matters (logic, problem, etc.). I would strongly suggest drill your math (e.g. https://www.preplounge.com/en/mental-math ), check the video of the calculation short cuts, read different example. 

Good luck,

Lucie

Was this answer helpful?

Ebru
Coach
on Feb 07, 2022
McKinsey|ex Firm Case Coach| LSE

Hi there,

First of all, you are not alone and there are many applicants who struggle with the math part.

The good news is that the math questions in the McKinsey interviews are not very hard or extraordinary.

What are the case books you are preparing with right now? You can find the best examples for the complexity level of the case math on McKinsey's website.

Another important aspect is to learn and develop an approach on how you will systematically and confidently walk the interviewer through your thought process. This way the solution to the math question won't appear too long, as the interviewer is not just waiting in silence for you to finish the whole calculation.

Feel free to reach out if you need more concrete help on this.

Good luck!

Ian
Coach
on Feb 08, 2022
Top US BCG / MBB Coach - 5,000 sessions |Tech, Platinion, Big 4 | 9/9 personal interviews passed | 95% candidate success

Hi there,

This is more of a problem on case leadership and structuring than it is on math.

Ultimately, you need to 1) Be clear on the objective and how what you're solving for will answer the question. Then 2) You need to figure out what numbers you have and how they fit in. Look at what might be missing and ask.

Feel free to reach out - happy to help with this.

Clara
Coach
on Feb 09, 2022
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut

Hello!

Have your tried GMAT materials? Particularly the integrated reasoning part can be very helpful. 

There are free exams in the internet that you can use for practice (the one of LBS MBA page, Verits prep, as well as some free trials for courses such as the one of The Economist (https://gmat.economist.com/)

Hope it helps!

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