Problem with Quant Questions

math MBB
New answer on Jul 16, 2020
7 Answers
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Anonymous A asked on Jun 26, 2020


While solving cases I noticed I was quite slow on the quant questions. I found this odd since math is my strong point. I suspect that I am not yet confident in driving the case in terms of finding what is quantitatively needed. Does the community have suggestions to help with my problem? Do I just need to practice more?

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Content Creator
replied on Jun 29, 2020
Top rated Case & PEI coach/Multiple real offers/McKinsey EM in New York /6 years McKinsey recruiting experience

Math in college is not the same as math when given in a case. The main difference being that case math requires understanding of context. This context is given in verbal form which you then have to interpret into an equation and solve accordingly.

This is why the best way to practice these problems is to use a GMAT type of book. Maybe read aloud the questions to yourself and then answer them. Once you get better at these then move on to real cases to further improve.

All the best,


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Content Creator
replied on Jun 28, 2020
McKinsey offers w/o final round interviews - 100% risk-free - 10+ years MBB coaching experience - Multiple book author

Hi Anonymous,

I common issue which I see for many of my coachees: it's a huge difference wheter to do a 'simple' pure math question stand-alone vs. solving a math question integrated in a complex case situation.

While for the pure math question you only need to do the numbers and execute, usually you first need to develop a conceptual approach first for solving a math question integrated into the case.

As we all know (but sometimes don't want to accept), the human brain is not capable of multitasking, but merely switching between different tasks sequentially. So trying to do the conceptual work at the same time as the pure math usually leads to wasting time (in case you do calculation and only understand later that your conecptual approach is wrong) and is definitely more prone to errors (multi-tasking...).

So I'd try to really separate those two steps and firstly do the conceptual work and also communicate that approach explicity to your interviewer, before secondly just executing the numbers!

Hope this helps - if so, please be so kind and give it a thumbs-up with the green upvote button below!


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Mohib replied on Jun 26, 2020

Hey! hope you're doing well and keeping safe.

I found myself in a similar situation - I was fairly strong at math having aced all math courses in college/university but for some reason I seemed to struggle with case math. Here are some tips that worked for me:

- Case math, conceptually, is rather basic. Its arithmetic after all, however the arithmetic difficulty is dialed to 11! You're dealing with large numbers (millions and billions) AND you need to be quick! I would recommend using the math tool on victor cheng's case interview website and practicing daily to deal with large numbers and to get better at both estimaton and exact answers

-Practice in front of a friend/family member! I can't stress this enough. Doing math on your own vs doing it infront of somebody sitting across and staring at you is a different ball game. Create an interview like environment and practice the quant with somebody sat across from you. This will help greatly with confidence. Walk your interviewer through your formula, reason for using the formula (logic) and then involve them in the calculation. Explain any assumptions. Basically get more comfortable communicating.your thought process.

Some other minor but helpful tips

-memorize your squares and cubes

-practice extensively with fractions, percentages (YouTube videos for shortcuts and drills)

Learn inverse numbers for e.g 1/6,2/6,3/6,4/6 1/7,2/7....1/8, for upto 11 - this will help improve your speed in mental math and consequently help you feel confident not to mention save time.

For finding the driving factors in any case my advice would be to follow up any WHY question with a HOW MUCH question. So try and quantify any information you get and get to a level, by practice ofc, where you are constantly switching b/w qualitative and quantitative analysis and supporting one with the other. Practice as many live cases as you can.

This is what worked for me, I am sure the experts would have much better advice. Hope this helps!

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Anonymous A on Jun 26, 2020

I will definitely incorporate these tips, especially practicing in front of other people. Thank you so much for the advice!! I sincerely appreciate it :)

Content Creator
updated an answer on Jul 02, 2020
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Best Rote Practice

Rocket Blocks:

Best Practice Strategy

1) Read the Economist (especially the daily graph and Financial Time frequently

2) Ask case partners to focus particularly on your math skills

Quant Tips

1) Make sure you understand the numbers

2) Remind yourself of the objective / hypothesis in the case, to see where this might fit

3) Find the differences - Where does change occur? The differences are what matter

4) Talk outloud while interpreting - first, it helps you think and process your thoughts, second, it lets the interviewer provide guidance and course correct if needed.


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Anonymous replied on Jun 30, 2020


I also suggest that GMAT is a good idea!



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Anonymous replied on Jun 27, 2020


You can try to practice on GMAT exercices


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Anonymous A on Jun 27, 2020

Will do, thanks!

Content Creator
replied on Jul 16, 2020
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut


GMAT unfortunately only gets better with practicing. Good news is that there are many ways of doing so!

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 (

Hope it helps!



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Udayan gave the best answer


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