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Mental math competition

fast math
New answer on Aug 31, 2023
5 Answers
Anonymous A asked on Jun 21, 2023

Hello guys,

do you know any similar websites where you can exercise your mental math, also with a ranking or something like that? I know that there is mental math at preplounge but i kinda feel like that there are coming always the same numbers, so it's getting kind of boring. But i also really enjoy it, i could improve my mental math a lot!


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Content Creator
replied on Jun 21, 2023
#1 rated MBB & McKinsey Coach

Hi there, 

Yes, you can use this:

It's basic and straight to the point. 

However - without knowing where you are in the process - most candidates need to work on their technique for approaching calculations, not on their speed. Speed actually matters little, but candidates surprisingly over-index for it. 

The most important thing is to make sure that you break down the problem into steps rather than doing it all at once. Building in buffers of thinking time in between the steps to minimize the probability of making mistakes and increase the chances of you correctly finding the most elegant approach. Happy to share a complementary guide on this - reach out. 


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replied on Jun 21, 2023
Bain | Roland Berger | EY-Parthenon | Mentoring Approach | 30% off first 10 sessions in May| Market Sizing | DARDEN MBA

Honestly… you don't get very difficult calculations in cases. No one asks you to calculate 132*38. And if you get those numbers, doing 130*40 (=5200) is just fine.

You have to be able to do 2 digit calculations relatively fast and accurately, but if you practice for a while in the preplounge tool you should be able to do it.

What you then need to do is not other tools. Is applying in practice, in quantitative problem solving.

Interviewers are NOT looking for people that can do complex math - they have excel for that - they are looking for people that can solve complex problems, quickly do an estimate or validate results delivered by an excel model.

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replied on Jun 28, 2023
BCG 1st & Final Round interviewer | Personalized prep with >95% success rate | 7yrs coaching | #1 for Experienced Hires
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Content Creator
replied on Jun 21, 2023
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Hi there,

My two favorite sites are:



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Content Creator
replied on Aug 31, 2023
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut


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 (

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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Cristian gave the best answer


Content Creator
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