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Anonymous A

on Dec 26, 2020

Global

Mental Divison Tricks

Hi Prep Lounge Community,

Happy Holidays!! Hope everyone is enjoying time with friends and family. Does anyone please have tips on dividing big numbers mentally. For example, 1241/17?

Many Thanks.

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Top answer

Ian

Coach

on Dec 26, 2020

Top US BCG / MBB Coach - 5,000 sessions |Tech, Platinion, Big 4 | 9/9 personal interviews passed | 95% candidate success

Happy Holidays!

First, you're not going to be asked to divide 1241 by 17. Now, let's go into tips/tricks for numbers you will see.

Key Tips/Tricks

Double/halve: You can adjust your numbers to be more manageable. For example, if I have 20 x 7, I can change that to 10 x 14. Much easier!

Split: 25 x 7 can be split into 25 x 5 PLUS 25 x 2.

Factor: Factor out numbers to allow for easier math.

Round then subtract: 29 x 9. Can do 29 x 10 MINUS 29

Long division/multiplication: You need to learn this. Some numbers will require it (yours for example)

Resources for Practice

Leverage the free preplounge resource:https://www.preplounge.com/en/mental-math.php

Rocketblocks is great for math in the context of a case: https://www.rocketblocks.me/

Print out math sheets for rote practide: https://www.math-drills.com/

1 comment

Anonymous A

on Dec 26, 2020

Thanks Ian.

Antonello

Coach

on Dec 27, 2020

McKinsey | NASA | top 10 FT MBA professor for consulting interviews | 6+ years of coaching

Hi,

My two main recommendations are:

1. Learn the results of the ratios from 1/2 to 1/20. Once you know this you can always round up to one of the ratios and solve the computation easily.

2. Practice with the Mental Math tool on PrepLounge after watching some YouTube videos on mental math. That really helps!

Best,

Antonello

1 comment

Anonymous A

on Dec 27, 2020

Thanks Antonello. Can you please give me an example of how you solve 7221/87 mentally using the ratio method. Many thanks for your time.

Gaurav

Coach

on Dec 27, 2020

#1 MBB Coach(Placed 750+ in MBBs & 1250+ in Tier2)| The Only 360° coach(Ex-McKinsey+Certified Coach+Active recruiter)

Hi there,

in addition to what Ian suggested, I can recommend you videos on mental math on Youtube and smartphone apps for practicing it.

Hope it was helpful,

Clara

Coach

on Dec 27, 2020

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

Hello!

Have you checked out the Mental Math tool in prepL? Is precisely aimed at this.

Cheers,

Clara

1 comment

Anonymous A

on Dec 27, 2020

Hi Clara. I've been utilising the mental math tool daily and I have improved significantly in additions, multiplications and subtractions thanks to it. However, I don't even know how to mentally approach the questions from the tool such as 7221/87. It takes me 60 seconds to solve a problem like that.