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

[@MConsultingPrep]

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

[@zenvd04]

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]

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

[@kgantshodii7258]

This is BOMB

[@areskonnor8448]

instablaster...

[@tebohomabuka6466]

Love this.

[@ehsansharif2296]

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

[@MConsultingPrep]

So glad to hear that ^^.

[@ZenityStudios]

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

[@MConsultingPrep]

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

[@TheCharlie2l]

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

[@FenceThis]

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

[@Rack979]

1.66 is almost 1⅔, that's 5/3! 5/3 x 3 is just 5.

[@alexandrahernandez6305]

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]

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

[@swarnapuri11]

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

[@junpyogoo6586]

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

[@MConsultingPrep]

Awesome!

[@trina7787]

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

[@NguyenPham-ih2hy]

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

[@MConsultingPrep]

Awesome! Thanks for the comment!^^

[@johnanon372]

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

[@omorontherun]

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

[@MConsultingPrep]

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

[@ianm1811]

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

[@MConsultingPrep]

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]

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

[@A7mad3emad]

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

[@MConsultingPrep]

Glad to hear that man ^^.

[@josemunozjlm]

eye opening! thank you! sharing and liking!

[@kiddclutch7679]

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

[@MConsultingPrep]

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! ^^

[@Vinan2k]

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

[@MConsultingPrep]

You're very welcome! ^^

[@trangta1589]

damn this is crazy! so easy and practical.

[@MConsultingPrep]

Awesome!

[@madk5864]

The adjustment's are difficult to determine

[@maxsparrowX]

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]

GOOD LUCKKKKKKK

[@Nonameviewer]

They should teach this at school

[@Dree2BeFree]

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

[@MConsultingPrep]

Glad you liked it! ^^

[@aleroma9236]

good job, good video, good method.

[@jensenraylight8011]

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]

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/

[@j.t.baustatik]

Thanks for sharing the tips

[@MConsultingPrep]

Any time ^^.

[@vuphuonganh9233]

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

[@MConsultingPrep]

We are glad that this video helps!

[@princedeux8923]

What a great video!

[@joewashington8703]

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

[@angieangie2505]

TG I am not the only one

[@ludgerderyce7312]

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

[@MConsultingPrep]

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

[@mikealike5000]

This man is a wizard

[@samael2135]

so did anyone actually get the answer in 5 seconds?

[@matthewli8028]

no

[@oceanheartz717]

Nope. I just panicked xD

[@MConsultingPrep]

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

[@anuraagsusarla1664]

Good approach!

[@neliswajokweni5872]

how did you go from 54 to 51 ??

[@MConsultingPrep]

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! ^^

[@BonelessSalmons]

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.

[@markdodson5432]

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

[@yequan3049]

Welcome back Kim

[@MConsultingPrep]

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

[@ucvutuan1164]

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?

[@jayasuryab8383]

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

[@whatamess8764]

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

[@annakaljob6005]

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

[@MConsultingPrep]

If you guys are in a hurry, watch this video: kzbin.info/www/bejne/d2rJqGmIaayWerM

[@HuyTran-vd8gj]

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

[@steffenhaldrupandersen2391]

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

[@vyche7882]

0.7 taken from 8.7 : 75 x 8.7

[@amaralikhan9906]

how to estimate the number of zeros taken away?

[@MConsultingPrep]

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. ^^

[@TheFuture36520]

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

[@MConsultingPrep]

Awesomeee^^.

[@roshnisomani6118]

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

[@ashishrsingh1104]

Thank you🤜🤛

[@Clementdijoux]

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

[@sayinmaster111]

How did you get the 0000s?

[@FM-dm8xj]

What do you mean take away 0's?

[@consideredthoughts1791]

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.

[@jubsology]

Welcome back

[@MConsultingPrep]

Glad to be back ^^.

[@rafaeltavarez4025]

Thank you for this

[@MConsultingPrep]

Awesome!!

[@yewut]

great vid, useful tips

[@MConsultingPrep]

So glad to hear that ^^.

[@michelleceline8655]

thanks!

[@Gorkhepilot]

Thank u soo much u r genious

[@MConsultingPrep]

I ... tend to agree :p

[@I_Arrived]

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

[@junglibra]

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]

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

[@sharonjuniorchess]

@@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]

Appreciate the straight and funny comment ^^

[@rafaella9700]

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

[@PS-ls3xy]

How much adjustment per decimal?

[@vnkc3880]

thanks a lot

[@MConsultingPrep]

You are most welcome^^.

[@raphaelkingen6945]

i dont understand why you dont round 76.928 to 77?

[@pierinapaytan6411]

How did you estimate the number of zeros taken away?

[@MConsultingPrep]

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. ^^

[@tittoairlangga7715]

This is so cool

[@MConsultingPrep]

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/

[@RobbieJ54]

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]

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). ^^

[@Uyinon]

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]

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 KZbin. Good luck🤗

[@MConsultingPrep]

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. ^^

[@chrisnacoustic1510]

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

[@FM-dm8xj]

How did u get 54-51?

[@uwu-xl8mm]

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

[@MConsultingPrep]

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]

I do the same or use a calculator

[@sanjeetsah9863]

Nice

[@MConsultingPrep]

yeap

[@usermusicej]

why did you adjust to 0.7 the 75?

[@MConsultingPrep]

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!

[@Skargar]

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]

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

[@vaidatul82]

RESPECT

[@MConsultingPrep]

You bet!! ^^

[@cuikane2444]

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]

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 ;)

[@joseochoa3571]

0.7 of 75... why?

[@victorhazel6349]

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]

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

[@uthmanodedele2220]

The problem is to remember the what u carried in ur head

[@tianz4710]

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

[@MConsultingPrep]

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.

[@MuneebAhmed-rk6rp]

The adjusting part is the main part of this video. It is not explained clearly. You could have shown the adjustment bar on each calculation. Could not fully grasp the idea.

[@Eliminator786]

Do you really need to be able to do this long multiplication questions in 5 seconds, in your head?

[@kienluu6430]

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

[@aabubakerr36]

How to take out zeros in multiplication part?

[@AbeNXC]

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]

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. ^^

[@andreslara9812]

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

[@MConsultingPrep]

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

[@andreslara9812]

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

[@anndee5426]

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

[@shade.9039]

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

[@lordbyron4147]

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

[@remfa4922]

huh

[@davidschneider3551]

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

[@MConsultingPrep]

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! ^^

[@aabubakerr36]

How did you take out zeros in multiplication part?

[@TheSharath4321]

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

[@Madalyn.Berger]

great vid, useful tips

[@Adrianna-Weeks]

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