Becoming a human calculator

I was recently watching a ted talk where a guy is multiplying multi digits on the fly and basically just flexing on calculator peasants like me. I'm going to try and learn the skill set for my job to double check my work and also any future tests I take like the GMAT. Wondering if anyone on WSO has attempted the same and has any tips on where to start (Online lectures, Books, etc.....)

21 Comments
 

Mental math can be improved upon if you dedicate time towards it. I've seen some friends do this to prepare for a coding competition but i don't know how much time and energy it would take.

 

One time in college I memorized a bunch of random double digit multiplication problem sets (32 x 37, 73 x 89, etc.)... fast forward a few months at a super day for banking at a BB, and one of the hardo MDs asked me one of these double digit math questions .... well it was one of the problems I memorized and you should have seen his face when I answered it within three seconds.... ahhhh good times, failed the rest of the super day horribly though.

 

You don't have to memorize to get these in ~5 seconds. Here is my strategy that I would use for both of these

32(40) = 128(10) =1280

32*3 = 96

1280 - 100 + 4 = 1184

73(90) = (70+3)9(10) = (630+27)10 = 6570

6570-70 = 6500 - 3 = 6497

Array
 

While I agree with everyone that it is really pointless, it can be learned. A quick way to get started is to look at a digital clock and do permutations of every basic (add, subtract, multiply, divide) calculation possible with the digits. I do this to fall asleep and have since I was a kid.

“The three most harmful addictions are heroin, carbohydrates, and a monthly salary.” - Nassim Taleb
 

If you are born with the talent or you already received training as a kid, it's a big plus, but I wouldn't suggest you spending time learning it now.

Being able to figure out within 3 seconds how much the price would change if cap rate goes from 5% to 4% is much more important.

 

Quis sed dolores dolor dolor. Molestiae dolor facilis nesciunt numquam sint voluptatem. Dolorem consequatur labore quibusdam cum quia vitae.

Voluptatem harum quia distinctio eius. Debitis distinctio qui in reiciendis. Consequatur quia eum quam earum.

Career Advancement Opportunities

September 2026 Investment Banking

  • Evercore 01 99.5%
  • Moelis & Company 01 98.9%
  • JPMorgan 01 98.4%
  • Goldman Sachs 01 97.8%
  • Morgan Stanley 07 97.3%

Overall Employee Satisfaction

September 2026 Investment Banking

  • Moelis & Company No 99.5%
  • Morgan Stanley 02 98.9%
  • Evercore 01 98.4%
  • Banco Santander 02 97.8%
  • BMO Capital Markets 12 97.3%

Professional Growth Opportunities

September 2026 Investment Banking

  • Evercore 01 99.5%
  • Moelis & Company 01 98.9%
  • Morgan Stanley 07 98.4%
  • Goldman Sachs 01 97.8%
  • JPMorgan No 97.3%

Total Avg Compensation

September 2026 Investment Banking

  • Vice President (16) $429
  • Associates (51) $260
  • 3rd+ Year Analyst (8) $210
  • 2nd Year Analyst (26) $182
  • Intern/Summer Associate (14) $159
  • 1st Year Analyst (84) $151
  • Intern/Summer Analyst (76) $101
notes
16 IB Interviews Notes

“... there’s no excuse to not take advantage of the resources out there available to you. Best value for your $ are the...”

Leaderboard

1
redever's picture
redever
99.2
2
Secyh62's picture
Secyh62
99.0
3
BankonBanking's picture
BankonBanking
99.0
4
kanon's picture
kanon
99.0
5
DrApeman's picture
DrApeman
98.9
6
dosk17's picture
dosk17
98.9
7
CompBanker's picture
CompBanker
98.9
8
GameTheory's picture
GameTheory
98.9
9
Betsy Massar's picture
Betsy Massar
98.9
10
bolo up's picture
bolo up
98.8
success
From 10 rejections to 1 dream investment banking internship

“... I believe it was the single biggest reason why I ended up with an offer...”