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Mental Math ressources

case math fast math math logic
Recent activity on Sep 01, 2023
5 Answers
2.5 k Views
Anonymous A asked on Nov 16, 2018

Hello,

Do you have any reliable (free online or book) resources to develop mental math techniques? I need a methodology and a way to progress.

Thanks in advance !

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Clara
Expert
Content Creator
replied on Sep 01, 2023
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut

Hello!

Precisely for the high amount of questions (1) asked by my coachees and students and (2) present in this Q&A, I created the “Economic and Financial concepts for MBB interviews”, recently published in PrepLounge’s shop (https://www.preplounge.com/en/shop/prep-guide/economic_and_financial_concepts_for_mbb_interviews).

After +5 years of candidate coaching and university teaching, and after having seen hundreds of cases, I realized that the economic-related knowledge needed to master case interviews is not much, and not complex. However, you need to know where to focus! Hence, I created the guide that I wish I could have had, summarizing the most important economic and financial concepts needed to solve consulting cases, combining key concepts theorical reviews and a hands-on methodology with examples and ad-hoc practice cases.

It focuses on 4 core topics, divided in chapters (each of them ranked in scale of importance, to help you maximize your time in short preparations):

  • Economic concepts: Profitability equation, Break even, Valuation methods (economic, market and asset), Payback period, NPV and IRR, + 3 practice cases to put it all together in a practical way. 
  • Financial concepts: Balance sheet, Income statement/P&L and Performance ratios (based on sales and based on investment), +1 practice case
  • Market structure & pricing: Market types, Perfect competition markets (demand and supply), Willingness to pay, Pricing approaches, Market segmentation and Price elasticity of demand, +1 practice case
  • Marketing and Customer Acquisition: Sales funnel, Key marketing metrics (CAC and CLV) and Churn, +1 practice case

Feel free to PM me for disccount codes for the guide, and I hope it helps you rock your interviews! 

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Anonymous replied on Jul 22, 2020

Hi A,

Here is math app for practicing math fractions and percentages from one of PL participant https://apps.apple.com/us/app/case-math/id1507653375?mt=8&ign-mpt=uo%3D4

Also, here is a tool provided by PrepLounge (https://www.preplounge.com/en/mental-math.php

And you can use Victor Cheng’s math tool and Magoosh's mental maths app, Mental math cards challenge app etc

Best,

André

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Vlad
Expert
updated an answer on Nov 16, 2018
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

Use math tools to train (Preplounge tool, Mimir math for iOS, Math tool on Viktor Cheng website). Train, train, and train again

Good luck!

(edited)

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Anonymous B replied on Nov 16, 2018
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Guennael
Expert
replied on Nov 16, 2018
Ex-MBB, Experienced Hire; I will teach you not only the how, but also the why of case interviews

caseinterviewmath.com, will rank you against other applicants by accuracy and speed. Do 10 to 15 minutes a day. You will see your rankings progress within just a few days.

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Clara gave the best answer

Clara

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McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut
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