Speed up Mental Math 5 times in 1 Week. It Works!

Рет қаралды 228,265

Күн бұрын

Are you unsure of how to master #consultingmath?
Are you struggling with complicated numbers?
Are you tired of doing quick big calculations?
If your answer is YES, then this #mentalmath video is definitely handcrafted for you!
If you wonder, I used to be you when I was a newbie in #managementconsulting! One of my biggest fears growing up was to be forced to do #mentalmath in pressured situations. I was really bad at negotiations that involved complicated numbers. I always got beaten in all mental math games. And… eventually, I forever failed and math was my biggest weakness.
But once becoming a #McKinsey #consultant by making the qualitative part compensate, the reality hit me hard, and I had no other options than to dominate all #consultingmath games.
So over time, I have developed a system of doing Math so fast in the head. After one week of intensive practice, and I became the fastest to calculate numbers among #consultants in the team. I even beat my own EM. So what’s the secret?
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Timestamps
0:00 Intro
1:23 What is Consulting Math?
2:26 Method to do Consulting Math
3:22 Multiplication type
8:33 Division type
11:26 Percentage type
14:30 Summary - Outro

Пікірлер: 154

@MConsultingPrep 8 ай бұрын

Feel free to ask any questions in our community where you can connect with other applicants and ex-consultants: mconsultingprep.com/community/

@ZenityStudios 4 жыл бұрын

most people know that 1.66 * 3 = 5 hahaha never knew anyone knew that

@MConsultingPrep 3 жыл бұрын

haha ^^ ... but you know that by now ^^

@TheCharlie2l Жыл бұрын

So sad.. I am in the non people category.

@FenceThis 6 ай бұрын

most people for some reason also happen to know that 3 * 17 = 51 or that 3 * 18 = 54 and that 3 * 19 = 57 dunno why

@zenvd04 4 жыл бұрын

For percentages, you can also break percentages down into ones and tens i.e. 32% is 10%x 3 and 1% x 2. So in the example above: 32% of 651,040 10% of 651,040 = 65104 = ~ 65,000 x 3 = 195,000 1% of 651,040 = 6510.4 = ~ 6500 x 2 = 13,000 Add that up and you get 208,000

@MConsultingPrep 3 жыл бұрын

This can work. My only concern is that there are just a bit too many steps ^^

@kgantshodii7258 3 жыл бұрын

This is BOMB

@areskonnor8448 2 жыл бұрын

instablaster...

@tebohomabuka6466 Жыл бұрын

Love this.

@ehsansharif2296 3 жыл бұрын

Mental math was my weak point. You saved my life! Thank you.

@MConsultingPrep 3 жыл бұрын

So glad to hear that ^^.

@swarnapuri11 Жыл бұрын

Thanks a lot for posting. Very clear explanation. Everyone should know this method. This should be thought in school.

@omorontherun 4 жыл бұрын

Ahh, finally you are back with some amazing tips bro.

@MConsultingPrep 4 жыл бұрын

Thanks, take a look at mconsultingprep.com/consulting-math/ for more on consulting math!

@junpyogoo6586 4 жыл бұрын

Thought I was hopeless in mental math until finding yours! Keep uploading great videos like this! Thumbs uppp

@MConsultingPrep 3 жыл бұрын

Awesome!

@Vinan2k 2 жыл бұрын

This is extremely well guided method...thank you very much!

@MConsultingPrep 2 жыл бұрын

You're very welcome! ^^

@NguyenPham-ih2hy 4 жыл бұрын

Glad you are back Kim, I was starting to run out of videos to watch... Great job on this one!

@MConsultingPrep 3 жыл бұрын

Awesome! Thanks for the comment!^^

@trina7787 Жыл бұрын

I dont understand how are you taking out zeroes in the multiplication part. can you please explain more on this?

@josemunozjlm Жыл бұрын

eye opening! thank you! sharing and liking!

@princedeux8923 Жыл бұрын

What a great video!

@trangta1589 4 жыл бұрын

damn this is crazy! so easy and practical.

@MConsultingPrep 3 жыл бұрын

Awesome!

@Dree2BeFree 2 жыл бұрын

This was such a cool way to explain things. thanks man

@MConsultingPrep 2 жыл бұрын

Glad you liked it! ^^

@markdodson5432 2 жыл бұрын

Kim, Thanks a lot for this video. Could you elaborate on the last adjustment there, bringing 217000 down to 210000? Thank you! Mark

@anuraagsusarla1664 2 жыл бұрын

Good approach!

@Madalyn.Berger 4 ай бұрын

great vid, useful tips

@A7mad3emad 4 жыл бұрын

This is extremely practical, thank you very much for sharing such techniques!!

@MConsultingPrep 3 жыл бұрын

Glad to hear that man ^^.

@alexandrahernandez6305 2 жыл бұрын

Great video. I am an industrial engineering student, yet I never had to challenge myself with mental math. My grandfather was very good at it given his years in sales. I have an interview approaching and this was good preparation.

@MConsultingPrep 2 жыл бұрын

Glad to hear that. Set a goal to beat your grandfather :p

@BonelessSalmons 2 жыл бұрын

how do you feel about using your multiplication trick iteratively? per your ex (1662 * 6514), you could narrow it down to (16.6 * 6.5), and then narrow it further to (17 *7). Then you can iteratively do it again, making it (1.7 * 7) => (2 * 7) = 14. adjust down to 12, add the single zero to equal 120. then adjust for the initial iteration and add all the zeros there for 11,000,000. is this too complicated? i'm asking because basic math like 1.66 * 3 = 5 is not in my wheelhouse at all, so I don't know how I would do (1662 * 6514) with the kind of accuracy you showed in your example.

@aleroma9236 2 жыл бұрын

good job, good video, good method.

@ianm1811 3 жыл бұрын

A better explanation on the downward and upward rounding during the multiplication portion would have been appreciated.

@MConsultingPrep 3 жыл бұрын

Hi Ian, Like I explained near the end of the video, it's like the feel you have when pressing more gas pedal going uphill. In the beginning, try ballpark them. With some practice, you will get the hang of it and your estimation will get better very quickly. If you want to be more precise, I explained in 5:15 about how to make a range ... Good luck with your practice! ^^

@PS-ls3xy Жыл бұрын

I agree... very poorly explained. The degree of the adjustment is not explained at all!

@j.t.baustatik 2 жыл бұрын

Thanks for sharing the tips

@MConsultingPrep 2 жыл бұрын

Any time ^^.

@vuphuonganh9233 4 жыл бұрын

Impressive Kim! Keep up the work, I am running out of time

@MConsultingPrep 4 жыл бұрын

We are glad that this video helps!

@mikealike5000 2 жыл бұрын

This man is a wizard

@madk5864 Жыл бұрын

The adjustment's are difficult to determine

@TheFuture36520 3 жыл бұрын

Thank you so much and I respect you for sharing what you love and can do 😍😍😍😃🙌🙌🙌🙌🔥🔥🔥🔥🔥🔥

@MConsultingPrep 3 жыл бұрын

Awesomeee^^.

@maxsparrowX 3 жыл бұрын

wish me luck dude, I just invited to do online MCQ test though I asked to enroll in 2022. Damn need to speed up my learning. Thanks for the nice vid

@MConsultingPrep 3 жыл бұрын

GOOD LUCKKKKKKK

@rafaeltavarez4025 3 жыл бұрын

Thank you for this

@MConsultingPrep 3 жыл бұрын

Awesome!!

@jensenraylight8011 4 жыл бұрын

Thanks for sharing this, The tips was very helpfull Yeah, i get fear too when get into the situation that require me to fast calculate I want to build confidence in mental math

@MConsultingPrep 4 жыл бұрын

Hi Jensen, We are so happy to hear that our video helps. For mental math, I recommend you to visit our website for more articles on that mconsultingprep.com/case-interview/, or take a look at our Math package designed for you: mconsultingprep.com/shop/consulting-math-drills-comprehensive/

@ashishrsingh1104 Жыл бұрын

Thank you🤜🤛

@johnanon372 2 жыл бұрын

Suggest another mental math method we do in China. 1700 * 40%, for example, can be divided into 1000*0.4+700*0.4 and further divided into 1000*0.4+100*0.4*7 which equals to 400+280

@ucvutuan1164 Жыл бұрын

If the question is like: "A were to grow by 5% per year in the future". Do you have any short cut to calculate A after 10 years? Or even a way to quickly calculate it without a calculator?

@kiddclutch7679 4 жыл бұрын

How do you adjust? It is difficult to grasp the adjusting part?

@MConsultingPrep 3 жыл бұрын

Hi Kidd, Like I explained near the end of the video, it's like the feel you have when pressing more gas pedal going uphill. In the beginning, try ballpark them. With some practice, you will get the hang of it and your estimation will get better very quickly. If you want to be more precise, I explained in 5:15 about how to make a range ... Good luck with your practice! ^^

@yequan3049 4 жыл бұрын

Welcome back Kim

@MConsultingPrep 3 жыл бұрын

Glad to be back. How long have you been a subscriber for?

@michelleceline8655 Жыл бұрын

thanks!

@tittoairlangga7715 4 жыл бұрын

This is so cool

@MConsultingPrep 4 жыл бұрын

@ludgerderyce7312 3 жыл бұрын

I think you just save me and bolster my weakness and I am only halfway through the video

@MConsultingPrep 3 жыл бұрын

What's the status now? Given that you are all the way through the video ;)

@roshnisomani6118 2 жыл бұрын

What do you mean by taking out zero? I'm unable to grasp that. Can you please help?

@victorhazel6349 2 жыл бұрын

Thanks for the video. Just a quick one, I'm trying to grasp what you meant by 7.8 is 2/3 from 8. Can you please explain that?

@MConsultingPrep 2 жыл бұрын

I mean ... 2/3 of 7 -> 8 ^^

@jubsology 4 жыл бұрын

Welcome back

@MConsultingPrep 3 жыл бұрын

Glad to be back ^^.

@HuyTran-vd8gj 4 ай бұрын

can I ask for clarification in the 5:30, how can we figure out 52 and then downgrade it to 51.5. Thank you very much

@samael2135 4 жыл бұрын

so did anyone actually get the answer in 5 seconds?

@matthewli8028 4 жыл бұрын

@oceanheartz717 4 жыл бұрын

Nope. I just panicked xD

@MConsultingPrep 3 жыл бұрын

Haha. You guys must have got them in like ... 6 seconds ^^.

@Skargar 4 жыл бұрын

Is there an app, where you can can be close to the result to a given percentage? Most that I find need an exact result, and then you end up doing small number stuff that's too easy.

@MConsultingPrep 3 жыл бұрын

This is such a great answer. I am building a tool. Please stay tuned ^^.

@joewashington8703 2 жыл бұрын

For the multiplication portion, I don't understand what you mean of taking the zero's out. Could you elaborate a bit more?

@angieangie2505 Жыл бұрын

TG I am not the only one

@Adrianna-Weeks 4 ай бұрын

We all don't get the job we love to do, atleast someone happy with what they do.

@PS-ls3xy Жыл бұрын

How much adjustment per decimal?

@Uyinon 4 жыл бұрын

Hello, thank you for this video. But i'd like to know how many zeros to take out? Do you know how many zero's to usally take out? i am not so good with maths, i can be better, but i need to get into McKinsey this year. Please help!

@elietecosta9564 4 жыл бұрын

Hello. I think the number of zeros you take depends on how comfortable you are with both 2 and 1 digit multiplication. You basically choose to take how many you need in order to perform the calculation quickly. I want to get into McKinsey this year as well. Hope your preparation is going well. You may want to check secrets of mental maths by Artur Benjamin here on KZfaq. Good luck🤗

@MConsultingPrep 3 жыл бұрын

Great question! Don't worry about this too much. The rule of thumb is to take out zeros until the numbers become (look) easy to digest. Even if you take out one too many or one to few, you will still do the steps and eventually add back the zeros like usual. The final result accuracy will not be affected (maybe just the speed). I myself often take out # of zeros so that what's left is something like ab x c (sometimes a x c). Hope this helps! Let me know if you have more questions. ^^

@Gorkhepilot 3 жыл бұрын

Thank u soo much u r genious

@MConsultingPrep 2 жыл бұрын

I ... tend to agree :p

@vnkc3880 2 жыл бұрын

thanks a lot

@MConsultingPrep 2 жыл бұрын

You are most welcome^^.

@amaralikhan9906 4 жыл бұрын

how to estimate the number of zeros taken away?

@MConsultingPrep 3 жыл бұрын

Don't worry about this too much. The rule of thumb is to take out zeros until the numbers become (look) easy to digest. Even if you take out one too many or one to few, you will still do the steps and eventually add back the zeros like usual. The final result accuracy will not be affected (maybe just the speed). I myself often take out # of zeros so that what's left is something like ab x c (sometimes a x c). Hope this helps! Let me know if you have more questions. ^^

@FM-dm8xj 3 ай бұрын

What do you mean take away 0's?

@andreslara9812 4 жыл бұрын

Hi Kim! One question, when you have to do both an upward and downward adjustment for multiplication, which one do you choose?

@MConsultingPrep 4 жыл бұрын

Do you mean when I “can” do either, which one do I prefer? Or do you mean something else? Thanks for asking^^

@andreslara9812 4 жыл бұрын

@@MConsultingPrep Lets say 789x7173. You round up 789 and 7173 down so its 8x70. What do you do in those cases?

@anndee5426 Жыл бұрын

@MConsulting Prep, can you answer this question please? :D

@shade.9039 9 ай бұрын

@@andreslara9812cancel them. Downward and upward adjustment so they cancel leaving you with 5600000

@Nonameviewer 5 ай бұрын

They should teach this at school

@steffenhaldrupandersen2391 2 жыл бұрын

Hi, I am not sure I get the 0.7 of 75 at 8:07. Could you please elaborate?

@vyche7882 2 жыл бұрын

0.7 taken from 8.7 : 75 x 8.7

@pierinapaytan6411 3 жыл бұрын

How did you estimate the number of zeros taken away?

@MConsultingPrep 3 жыл бұрын

@neliswajokweni5872 4 жыл бұрын

how did you go from 54 to 51 ??

@MConsultingPrep 3 жыл бұрын

Hi Neliswa, you are probably asking the question of: How to properly do the Adjustment? Like I explained near the end of the video, it's like the feel you have when pressing more gas pedal going uphill. In the beginning, try ballpark them. With some practice, you will get the hang of it and your estimation will get better very quickly. If you want to be more precise, I explained in 5:15 about how to make a range ... Good luck with your practice! ^^

@tianz4710 4 жыл бұрын

when rounding 1234 and 567, why did 1234 become 12.34 rather than 1.234? which will give quite inaccurate answer.

@MConsultingPrep 4 жыл бұрын

Hi Tian, interesting question. I am glad you asked. Basically we can both do 12.34 x 5.67 or 1.234 x 56.7. The point is to take out "enough" zeros to make it easy to calculate but not too much to make the error margin too high. To me, with multiplication, I can easily do double-digit x single-digit so this is the way to go for me.

@Clementdijoux Жыл бұрын

I don't understand how do you put aways "zero" like why sometimes you have 4 zeros and sometimes you have 6

@rafaella9700 Жыл бұрын

This Is not as Easy as you think It Is lol but thank you! Gonna keep practicing

@FM-dm8xj 3 ай бұрын

How did u get 54-51?

@vaidatul82 2 жыл бұрын

RESPECT

@MConsultingPrep 2 жыл бұрын

You bet!! ^^

@dr.sarah894 5 ай бұрын

I have challenge to beat my friend thank you thank you

@xkells757 3 жыл бұрын

Watching this and realizing that I'm f**ked for interviews... Are you doing all the steps in your head or jotting down notes? I'm struggling to keep all the zeros in my head while I do other calculations.

@MConsultingPrep 2 жыл бұрын

In the beginning, feel free to use paper. In fact, you can totally use the scratch paper in case interviews. As you get used to it, practice without paper too. It's a good tool to have (being able to boom boom in your head). ^^

@whatamess8764 3 жыл бұрын

ahhhhhhhhhhhhhhhhhhhh.... i am so unprepared for my consulting interview later this week

@annakaljob6005 3 жыл бұрын

SAME I have an consulting interview in 6 days. Noway I'll get it

@MConsultingPrep 3 жыл бұрын

If you guys are in a hurry, watch this video: kzfaq.info/get/bejne/d5-WqpmDma3HdIU.html

@sanjeetsah9863 3 жыл бұрын

Nice

@MConsultingPrep 2 жыл бұрын

yeap

@I_Arrived 4 жыл бұрын

@8:02 But what if you are still shit at math and can't do 72*8?

@junglibra 4 жыл бұрын

You may wanna go back at 7:50 and realize it’s common to know 75*2=150. Otherwise you may still round it as 70*8, make a calculation of 7*8=56, return 1 zero, we get 560, and adjust, we have around 580. Dont you wanna say that you dont even know 7*8?

@Skargar 4 жыл бұрын

do 8*8=64, 640-8=632

@sharonjuniorchess 3 жыл бұрын

@@Skargar That's an 8% error the sum is (80 x 8) - (8 x 8) = 640 - 64 ≈ 570 To reply to Eric's question: You could try learning to do mental multiplication left to right as it allows you to do your sums in stages: 72 x 8 = 560 + (2x8) = 576. Vedic multiplication uses this approach putting slashes between the 10's columns (although I prefer using commas) which allows you to have more than one digit result in a particular column and do the carry as you go along. So 72 x 8 becomes 56/16 = 576. The more you practice the easier it gets. Because vedic maths handles multiplication left-to-right you only need to do two digit multiplication by two digit to get within 5% accuracy and the steps only need to be followed to get the first two result digits (which is just three multiplication operations). For example: 23 x 87 = (2x8) , [(8x3)+(2x7)] , 0 = 16 , [24+14] , 0 = 1980 (98.95%) to get 100% add on 3 x 7 = 21.

@MConsultingPrep 3 жыл бұрын

Appreciate the straight and funny comment ^^

@AbeNXC 3 жыл бұрын

For the answer where you found it to be 660 mil. Wouldn’t being off by 8,000,000 significantly mess up later calculations?

@MConsultingPrep 3 жыл бұрын

In most consulting contexts, 5% margin is acceptable. In some special cases where the interviewer needs you to be more correct, he/she will tell you. It's often beneficial to trade a little accuracy for much higher speed. ^^

@joseochoa3571 Жыл бұрын

0.7 of 75... why?

@usermusicej 10 ай бұрын

why did you adjust to 0.7 the 75?

@MConsultingPrep 10 ай бұрын

Hi there, The reason why we adjusted to 0.7 of 75 because we have round up the number 8.7 to 8.0, thus we need to "compensate" by multiplying 75 by that 0.7. To simply visualize, the formula goes like this: 75 x 8.7 = 75 x 80 + 75 x 0.7 Hope it helps!

@consideredthoughts1791 Жыл бұрын

If each of these calls take the 5 seconds allowed, a calculator is likely to be much faster, and more accurate. In fact, I was able to do the multiplication ones in prob half that time on the calculator. Of course, you need a calculator to hand in the first place but if you have one, it's often faster than these techniques.

@uwu-xl8mm 3 жыл бұрын

couldn’t do mental math but could quickly solve it through jotting down... maybe i’m really hopeless

@MConsultingPrep 3 жыл бұрын

Nah you are NOT! Have a little faith and keep practicing it. Btw, it's ok to jot down a few numbers during case interviews ... as long as you still do it fast! ^^

@priyankadey2620 2 жыл бұрын

I do the same or use a calculator

@aabubakerr37 Жыл бұрын

How did you take out zeros in multiplication part?

@chrisnacoustic1510 Жыл бұрын

Putting away "zeros". My question is: where the hell are the zeros??? How many zeros should I take??

@ivantulumovic861 2 жыл бұрын

Sry but I dont get any of this

@fuckaII Жыл бұрын

The first shit i could do it in 4 secs mentally easily 8910×547

@cuikane2444 8 ай бұрын

Maybe I'm dumb, but there is no way I can calculate the examples in just 5 seconds, on avg they took me like 20-30s

@MConsultingPrep 8 ай бұрын

You do not need to be accurate for those mental math. The idea here is that: you just need to get the approximate number, because in real consulting world you will need to estimate a lot. So try my methods to practice and estimate faster ;)

@kienluu6430 Жыл бұрын

the method is fabulous, but im still can not caculate them just in 5 seconds, hic

@aabubakerr37 Жыл бұрын

How to take out zeros in multiplication part?

@remfa4922 3 жыл бұрын

huh

@lordbyron4147 3 жыл бұрын

how in the name of fuck is this faster than a calculator

@davidschneider3551 3 жыл бұрын

i think this does not work at all, by the way is needed 25 seconds for the answer and got 760 million ;)

@MConsultingPrep 3 жыл бұрын

If you have a little more faith in it and practice more, David ^^. I have seen so many people succeeded with it ... It will work! ^^

@TheSharath4321 3 жыл бұрын

I got one more trick for multiplication adjustment guys. Lets say 91847*63291 make it smaller numbers like 9.18*6.32 now round this number downwards 9*6=54 Now adjustment part. Take 1 from (9.1