Use this simple math rule to make better decisions – it’s hiding in plain sight, says the best-selling author

Do you want to make better decisions in your life and workplace? Turn to math, says Hannah Fry.

British mathematician, professor and bestselling author writes and speaks about how simple math can benefit people’s everyday lives. There’s a mathematical way of looking at “almost everything,” she told CNBC Make It.

The trick is to get people to see those connections. “The math you learn in school is so, so different from what the real subject is,” Fry said. “You leave school thinking that math is that subject in those dusty books, over there in the corner.”

Fry’s goal is to change that mistake. She points to a unique mathematical concept — known as the Fermi problem — as a great way to understand how a little math can change the way you make decisions.

Highly successful people – from CEOs to other leaders – know how to leverage the information they have to make great decisions. Here’s how to do it, says Fry.

The Fermi problem may be familiar, because it is popular in practical questions. Here’s an example: How many piano players are there in Chicago?

Learning how to answer that kind of question means developing an important success skill, Fry said: making quick, accurate judgments. This technique is named after the 20th century physicist, Enrico Fermi, who had the remarkable ability to make sophisticated calculations based on very small data.

In one of his most famous examples, Fermi — who created the world’s first nuclear reactor — accurately estimated the power of the atomic bomb before anyone had “an idea” what power it would be, Fry said.

Before the Manhattan Project’s first nuclear test, Fermi grabbed a piece of paper and tore it up. He took the pieces out of an observation tower as the test began, and tracked their progress before landing.

Observing those distances is enough to estimate the tonnage of the final bomb, Fry said. Fermi found the one equation he knew, and expanded outward from there.

So, how many piano players are there in Chicago?

Start by breaking it down. How many have a piano in their house? How often will this piano need to be played? How many pianos can one player repair in a day?

Unlike the big question, these little things have meaningful answers: You can research Chicago’s population, find statistics on the average number of pianos per household and learn how often the average piano needs to be played.

“All of a sudden, you have this idea of ​​needing to play the piano in Chicago … and that process involves all kinds of different things,” Fry said.

You can apply the same principle to real-world examples, too — apply some healthy skepticism to numbers you’d take for granted.

When Fry saw figures about how long it would take to close the gender pay gap, for example, she did her own mental math to see if her best guess matched the experts’ findings.

Likewise, if you’re in a staff meeting and you notice that some of the numbers in the presentation look a little off, raise your hand. Or, apply more analysis to the numbers behind big life decisions – like calculating how long you can live without your savings, before you quit your job.

“It’s very useful when it comes to looking at you and deciding whether you believe the numbers you’re seeing,” Fry said.

That helps you make confident decisions, especially if your choices go against conventional wisdom, she says.

“If you look [even] The numbers that we only see in the news, having these little tricks in your pocket can help you be a little more skeptical about the numbers around you,” she said. “You’ll realize how real many of these numbers are. Just educated guesses.”

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