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how to Improve math skills

Actively preparing for interviews with McKinsey
New answer on Jul 08, 2020
3 Answers
1.2 k Views
asked on Jul 07, 2020
Only advanced candidates with scheduled interviews please

Hi there,

So i have been doing few cases with peers and it's clear that math is an issue for me. I have an applied math backgroup so i understand the concepts fairly well. I am usually also good in getting the math structure, however I have been using calculators and excel forever and I am facing the following problems :

1- struggles in presenting my calculation. I have tendency to go and try the numbers, then add other numbers, rather than lay down the whole structure before calculating (I actually have the same tendency when i am doing the structure of the case study. This manfests itself as follows: I have the intuiton that some combinatin of numbers will get me somewhere, so i do the computation then decide my next step rather than the opposite. Example : a graph shows me the monthly average skier days, then nb of skiers, then i have an info about the spending of a skier.

Instead of saying Annual revenues = (sum of the monthly averge skier days ) x nb of skiers x spending per day, I have tendany to start doing computation after computation and once i get the result of one, it gives me hints about the next computation to take. My usualy way of doing this would look like "I am gonna sum the averges of each months". Once i get the result, I will say "now i am gonna multiply it by nb of skiers so i have the nb of skiers per year" and once i get that result I will say "Now i am gonna multiplay by $150, in order to get the total revenues"

2. I am still struggling in finding a clear way to lay out my calclations on my notes. It makes it stressful for me and impossible for the interviewer to follow me. it also makes it harder sometimes to come back to a given number.

I have a good memory and rely a lot on my memory to find myself though my own mess, but it's clearly not the way to go if i want to improve

3. finally nb2 also contributes in me making some mistakes sometimes. I dont think i did one case without doing at least one mistake

4. when doing peer practice cases, i realised that i am slower than most other people.

I bought V. Cheng math courses and went thruogh the material, I am also practicing basic mental math using a app on my phone. I am also trying to re learn the multiplication tabel to get things faster. I have also bought a book called Secrets of Mental math but i havent gone through that one yet

Any tips on how to improve ?


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Anonymous replied on Jul 08, 2020

Dear Rafic,

For practicing and improving your mental math you can find also some apps and tools, besides Victor Cheng’s math tool (Magoosh's mental maths app, Mental math cards challenge app etc). But there are some facts that will help in overall improvements:

• Consulting math is a very different than academic math. Working consultants - and consulting interview candidates - are always under time pressure. Results are what matter and answers are required simply to be good enough to guide business decisions, rather than being absolutely correct.

• The next important thing is that rather make it on the paper to structure the notes and then to communicate the results clearly rather than make your calculations fast

• The time pressure in case interviews is severe and you cannot afford to waste time. But to make your calculations right you shouldn’t be in a rush. So, I would recommend you here to work on both - practice with time limitations and learn how to keep your mind peaceful and concentrated (it might be not so popular advice here, but mediations really make their job here ).

• Be comfortable and confident to state your answers not as a questions. Interviewers notice this, and this will not give a credit.

If you need any further help or career advice, feel free to reach me out.



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Anonymous updated the answer on Jul 07, 2020

Hi Rafic - congrats on getting through to interviews!

Case interview maths is one of the few aspects which you can 100% crack with sufficient practice. Two things to consider:

- Think about case interviews as high-school algebra questions. First step is to write down what you think the algebraic equation will be. Practicing with an experienced coach can help on this. Also reading through model answers to different cases. Rememeber McK first round interviews are highly structured and typically interviewer led which will help

- Secondly, I would not dedicate time for mental maths / memorizing fractions or tables at this stage. This is a nice to have skill but effectively writing a structure for your approach is core

In addition to practicing writing the equations - do math drills. Effectively a refresher on how to do high school additions, subtractions, multiplications and long division. 10 minutes a day will see you through. Various online portal provide these. Happy to discuss further if helpful


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raf on Jul 07, 2020

Thanks Sunaina, can you recommend me any of those online portals ?

Anonymous on Jul 07, 2020

Unfortunately Preplounge guidelines mean I cannot give the link but if you search for them - there are loads

Content Creator
replied on Jul 08, 2020
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut


I struggled with the same thing.

I would strongly recomment you practice it with the Integrated Reasoning part of the GMAT exam.

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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