Mental Math ressources

case math fast math math logic
New answer on Jul 22, 2020
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Anonymous A asked on Nov 16, 2018


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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Anonymous replied on Jul 22, 2020

Hi A,

Here is math app for practicing math fractions and percentages from one of PL participant

Also, here is a tool provided by PrepLounge (

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



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Content Creator
updated an answer on Nov 16, 2018
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School


Basically, you need to develop 3 calculation skills:

1) Learn how to multiply double digit numbers (

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


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!


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