Ways to improve mental math

[DukeEsquire]

Background: I recently interview with McKinsey & Co. for a consultant position. McKinsey--if you don't know--is widely considered far and above the best consulting firm in the world and they work with the largest companies in the world.

Most consulting firms hire exclusively from business schools, but McKinsey is relatively unique in that they hire extensively from top PhD, MD and JD programs in addition to MBA programs. Their theory is they just want the smartest people in the world working for them and they will figure out how to use them down the road.

The interview process, for non-MBAs, is a three round process using tests, case interviews and estimation problems. They don't use the typical "Tell me about a time that you had to overcome a barrier" type BS questions.

My problem is that both case interviews and estimation problems reward people that are very good at mental math.

Due to my slow math abilities--I haven't taken a math class in nearly 7 years--I didn't get past the second round of interviews.

Question: What are some good ways to learn mental math? I need to improve my math skills in multiplication, division, ratios and percentages. Not particularly complicated math, but I need to improve it.

Are there any websites or phone apps or programs that people recommend?

[Rudy]

practice

[Flawed]

Math is just like any other problem solving task; it's all about strategy. Those with the better strategies are seemingly more adept at mental arithmetic.

The more efficient the strategy, the better you will be at it. You might want to start with the basics such as number bonds if you don't have much education in the subject.

[hougtimo]

The best way to improve your maths is use it. I used to work in a convenience store. Instead of having the till work out the change for me, I used to do it in my head. The result? Addition, subtraction, multiplication and division are now easy to do in my head. Simples.

I was also taught that Mathematicians are lazy. Always use the easiest way to work something out - not the 'correct' way by the book.

[Davo]

Break down the process and use shortcuts for what you already know.

14% of 100 is 14 because there are 14 pennies out of 100 in a dollar

1/4 of 64 is 16 because 64 divided by 2 is 32, and 32 divided by 2 is 16. 1/4 is simply 1/2 of 1/2.

100 times 30 is 1 times 3, and then add 3 zeros to the end.

365 plus 135 equals 500 because 65 + 35 is 100, then + 300 + 100.

[hougtimo]

100 times 30 is 1 times 3, and then add 3 zeros to the end.

I have to disagree with this. While it will get the correct answer, it's much better to understand where the decimal point goes (or, in this case, doesn't go) and why. Otherwise it'll just cause problems later on.

[Davo]

I have to disagree with this. While it will get the correct answer, it's much better to understand where the decimal point goes (or, in this case, doesn't go) and why. Otherwise it'll just cause problems later on.

Well that's assuming that a lawyer already has a grasp of Base 10.

[dknm]

TTC has some videos if you learn better that way.

Speed comes with practice. Take an 8-grader's book and work from it ...

[Phouchg]

There's a Math Workout app on Android (probably on other systems, too). It's addictive.

[The Teej]

There's a Math Workout app on Android (probably on other systems, too). It's addictive.

That's really good. I just tried that out... keep getting rinsed on the I'm Feeling Clever mode, even after rinsing Add/Subtract and Multiply/Divide sections! lol

[Teebor]

practice and repetition as most have already said, example is when I worked in a casino I could do all kinds of math really easily. Now however I work with networks so my binary math is pretty good (subnetting etc) and my hex is reasonable, however I cannot do the same level of math I did as when I worked in the casino.

In some respects because of this I feel I've let my mind relax too much but in other way I stress it a lot more with problem solving and practical problems :shiftyninja:

[+Majesticmerc MVC]

Their theory is they just want the smartest people in the world working for them and they will figure out how to use them down the road.

Is it just me, or does that sound like a horrible recruitment strategy? Sounds like they're just trying to pool talent and give them substandard jobs just to avoid the competition getting them :/

[Zain Adeel]

leave it all.. there is one simple way to make it happen..

just dont use the calculator alot...

ive started doing most of my calculations in my head just to see if i can do them correctly with speed and i am right 80% of the time.. i recheck with calculator..

I am doing ACCA. and i have made this a practise so during exams i can do the simpler calculations in my head and save time. And also you feel good when you get a big equation correct in ur head :p

[DukeEsquire]

Is it just me, or does that sound like a horrible recruitment strategy? Sounds like they're just trying to pool talent and give them substandard jobs just to avoid the competition getting them :/

Well, it's working for them. Smart people are always useful assuming they don't have some terrible counter-balance like a drug addiction, laziness etc. Consulting is all about helping people solve problems and these problems can range from finding new customers to reducing headcount to raising profits...etc.

The theory is you can teach people business concepts, but you can't teach inherent intelligence. So, find smart people in any field and teach them business concepts.

Believe me, it's hardly a "substandard job". It challenging for even the smartest people because you can to go to a company and tell people who've been running the company for decades ways they can improve their system.

Thanks for all the advice from people that said to practice more, but I was hoping to get more specific information.

I'm looking for an app or program that I can sit at my desk after work to improve my mental math. I don't really use math in my daily life as a lawyer.

[Growled Member]

The best way to improve your maths is use it. I used to work in a convenience store. Instead of having the till work out the change for me, I used to do it in my head. The result? Addition, subtraction, multiplication and division are now easy to do in my head. Simples.

I was also taught that Mathematicians are lazy. Always use the easiest way to work something out - not the 'correct' way by the book.

I agree. I'm very good at mental math and I found a way that works for me. The best way to improve is just use it daily. For example, 32 x 23, I'd say 32 x2 which is 64 x 10 which is 640 + 32 x 3 which is 96 and 640 + 96 = 736.I've done it so long I can do it much faster than most people can do it on a calculator. It just takes practice.

[Chip201]

I have practiced a lot on calculationrankings.c, it was a lot of help,

Good luck Chip

[sakshi]

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The best part about mathematics is that it can be used in your daily life pretty easily. 

UCMAS provides Abacus-based mental math program for children aged 4-13 years which  develop some amazing mental math skills. Children who learn Abacus calculations can easily conquer their fear of math. It enables them to confidently solve math questions in exams. This newly developed confidence also helps them to ace at other subjects in school.