Best resources for math improvement? (for a complete number novice!)

fast math math mental math Quantitative skills
Edited on Sep 05, 2021
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Anonymous A asked on Aug 22, 2019

Whilst the preparation for case studies is going okay, I hit huge hurdles when I hit numbers.

I am looking for resources that will help me start from the very basics when it comes to mental math.

I have come across Victor Cheng's course https://www.caseinterview.com/mental-math (though his 'ultimate' option is way out of my budget!) and FastMath course. Does anybody have any reviews or recommendations on courses to take to improve mental math, please?

https://www.caseinterview.com/mental-math

Thank you in advance!

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Vlad
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replied on Aug 22, 2019
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School

Hi,

Basically, you need to develop 3 calculation skills:

1) Learn how to multiply double-digit numbers (https://www.youtube.com/watch?v=6ndkkPZYJHo).

2) Learn how to work with zeros. Best way - always use 10^power instead of zeros

Example:

300x9000 = 3*10ˆ2 x 9*10ˆ3=3x9*10ˆ(2+3)=27*10ˆ5

Handwritten it looks not that complicated. If you get used to writing all the numbers that way, you will never loose zeros and all multiplications/divisions will be replaced with + or -.

3) Learn the division table up to 1/11 (i.e. 5/6 = 83.3%). It will help you calculate any percentage problems. For example, if your market is $620M and your revenues are $51M you can use 5/6 as a proxy to calculate the market share

Good luck!

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Anonymous A on Aug 22, 2019

Thank you! Do you have any opinions or experiences on the Fast Math course, or Victor Chen's Mental Math Fast course?

Anonymous B on Aug 22, 2019

What is the division table? Do you have any links that teach this?

Antonello
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replied on Aug 31, 2020
McKinsey | MBA professor for consulting interviews
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Marco-Alexander
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updated an answer on Sep 05, 2021
Former BCG | Case author for efellows book | Experience in 6 consultancies (Stern Stewart, Capgemini, KPMG, VW Con., Hor

(edited)

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

Hello!

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 (https://gmat.economist.com/)

The (old) McKinsey PST, BCG Online Test, Bain SOVA test, etc. are all quite similar so leverage resources across all of them.

https://www.myconsultingoffer.org/case-study-interview-prep/bcg-online/

https://www.shl.com/shldirect/en/practice-tests

https://www.psychometricinstitute.co.uk/Free-Aptitude-Tests.asp

Hope it helps!

Cheers,

Clara

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Anonymous replied on Aug 22, 2020

Hello, A!

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 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.

Generally, to practice your quantitative skills I would recommend different math, logic, and verbal tests on https://trytalentq.com/how-to-prepare/# and then select "Elements Practice Test".

You don´t need to learn them by heart, rather skipping through to get a first impression and a better understanding

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

Best,

André

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Vlad gave the best answer

Vlad

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