AI cannot replace business math

Large language models excel at academic math and win competitions, but business math is different. It requires practical, approximate solutions to fuzzy, fluid problems that expose AI's weak points.

Math is the core language of business

Business leaders across all functions and levels must speak math fluently. Paraphrasing Charlie Munger: Making business decisions without knowing the numbers is like fighting with one leg tied behind your back.

“Making business decisions without knowing the numbers is like fighting with one leg tied behind your back.”

You don't need to be a math genius

You don't need to solve differential equations to speak useful business math. You must structure and solve real-world problems in practical and flexible ways. Like any language, it's learnable and use it or lose it.

Inattentional blindness blinds managers

In the dot-com boom, managers obsessed over eyeballs and missed the gorilla in the room: cash flow is necessary to create business value. Simple calculations showed the math didn't add up.

Scott McNealy saw through the hype

Scott McNealy, then CEO of Sun Microsystems, used elementary reasoning to show that many widely-accepted core assumptions in the dot-com era were ridiculous. His post-mortem: What were you thinking?

“What were you thinking?”

The 2008 financial crisis proved it again

Experienced analysts rated Lehman Brothers as buy stocks and A grade credit risks weeks before collapse. Michael Burry did basic math on home-loan securitization and concluded: This makes no sense. He was correct.

Bill Gurley's Uber lesson

Venture capitalist Bill Gurley's 2014 memo showed experts appraising Uber's value had the world's best financial model, but core assumptions were off by a factor of twenty-five times. History validated his reasoning.

Always do your own sanity check

It's easy to blindly trust detailed numbers from fancy models. But that's no replacement for thinking and reasoning for yourself. Better to be approximately right using your own mind than precisely wrong using flawed outputs.

“It is better to be approximately right (using your own mind) than precisely wrong (using flawed model outputs).”

Build numerical intuition

Use an unusual calculator that thinks only if you think too.Enter a calculation and it asks for your rough best-guess answer first.If your estimate is in the right ballpark, it gives the exact solution.

Learn the McKinsey method

The legendary McKinsey method works by iteratively building, testing, and refining simple hypotheses using relevant facts and approximate math. It applies to virtually any problem and is a learnable problem-solving framework.

Master mental-math strategies

Sanjoy Mahajan teaches six practical strategies to simplify complex problems: dimensional analysis, easy cases, lumping, picture proofs, successive approximation, and reasoning by analogy. These tools apply across business situations.

Decisions and outcomes are not the same

In an MBA finance class Oil Baron game, only twenty percent of students made the mathematically correct decision every time. Yet some who gambled ended up with more wealth through sheer chance. Decisions aren't outcomes.

“Decisions aren't outcomes.”

Probabilistic thinking beats gambling

The best-decision cohort clustered around the top ten to fifteen percent of final wealth.Gambling creates outlier winners but mostly creates busts.Using probabilistic logic with the best inputs remains the best way to make good decisions.

Linear thinking fails on non-linear problems

Physics Nobel laureate Murray Gell-Mann and Ole Peters showed that while average outcomes for millions of theoretical players are positive, any individual single player goes bust with near one hundred percent certainty.

The Kelly Criterion sizes bets smartly

To maximize long-term growth rates, one must smartly size bets.Kelly's math optimally sizes them to avoid game-over strikeouts while still swinging for home-runs on juicy pitches where you have a big edge over the odds.

Numbers must mix with words

Statistician Hans Rosling said our beautifully complex world cannot be understood by words alone. Numbers must always be in the mix. Business leaders must speak fluent math to lead effectively in any era.

“Our beautifully complex world cannot be understood by words alone, numbers must always be in the mix.”