From the number that defeated the Nazis to the one that put a smile on the faces of drunken sailors, here are 10 digits with real value.
1. Nine-tenths of a cent: The fraction that makes us pump more gas
Every time we fill up our tanks, we wrestle with one of life's thorniest mysteries: Why do gas prices end in 0.9 cents? Unfortunately, the origins of the increment are murky. Some sources attribute the practice to the 1920s and 1930s, when the gasoline tax was nine-tenths of a cent.
Stations would simply slap the extra 0.9 onto the advertised price of a gallon to give Uncle Sam his cut. Others theorize that slashing 0.1 cent off the price undercut competitors back in the days when gas was just a few cents per gallon.
Although most drivers simply ignore the extra 0.9 cents, oil companies certainly don't. In 2009, Americans consumed 378 million gallons of gas per day, and that extra 0.9 cents per gallon was collectively worth nearly $3.5 million a day. On the flip side, you could also argue that customers collectively saved around $340,000 per day, thanks to stations' reluctance to round up to the next penny.
2. 2.3 milligrams of B1: The recommendation that won a war
Food nutrition labels were originally designed to do a lot more than make you feel guilty about eating Cheetos. The dietary recommendations were created in the 1940s to help America accomplish one of the most important missions in its history -- defeating Hitler.
On the brink of entering World War II, U.S. military leaders discovered an unexpected problem. Our soldiers weren't only hungry for victory; they were just plain hungry. After screening some 1 million young men for potential service in the armed forces, the Selective Service discovered that about one in seven candidates suffered from "disabilities directly or indirectly connected with nutrition." The recruits were unfit for duty, and the nation needed a way to turn these malnourished men into Axis-pummeling Captain Americas.
The administration pounced on the problem. President Franklin Roosevelt gathered a committee of nutrition experts to create a practical diet that would keep Americans in shape -- both at home and while fighting abroad. Within months, the committee released its "Recommended Dietary Allowances" for each nutrient. For example, a "very active" man would need 2.3 mg of vitamin B1 per day, while a "very active" woman would need about 1.8 mg.
The system worked, and today, the recommendations have morphed into the nutrition labels now standard on packaged foods. Every few years, the numbers are revised and expanded to reflect new developments in nutrition science, and they've picked up the snazzy name "Dietary Reference Intakes." But don't be fooled by the titling. At their core, they're still the same recommendations that helped a nutrient-starved nation defeat the Nazis.
3. 55 mph: The speed that drove America crazy
During the oil crisis of the 1970s, the U.S. government was desperate to convince Americans to burn less gasoline. Realizing that cars are more fuel-efficient when driven at lower speeds, Congress decided to force people to drive slower. In 1974, it enacted a law that set the national speed limit at 55 mph, along with a threat: Any state that didn't comply with the rule would lose its federal highway funding.
So, did the lowered speed limit actually accomplish its goal? The answer is still hotly debated. While the law did slash petroleum consumption by 167,000 barrels per day, the savings represented a drop in demand of only one or two percent. Highway fatalities also dropped significantly with the lower speed limit, though some analysts have theorized that this reduction was the result of a general decrease in recreational driving rather than slower speeds.
Nonetheless, both state governments and average citizens whined about the law so much that Congress bumped up the speed limit to 65 mph in 1987, then did away with the law completely in 1995, putting speed limits back in the hands of the states.
4. Five seconds: The rule that can make you sick
At some time or another, with or without witnesses present, we've all used the five-second rule to justify eating a cookie that's touched the floor. After all, everyone knows that if a tasty treat spends less than five seconds on the ground, it doesn't collect germs.
Well, not exactly. In 2003, high school student Jillian Clarke performed the first known scientific tests on the five-second rule. While interning at the food science laboratory at the University of Illinois at Urbana-Champaign, Clarke tested the theory by placing gummy bears and cookies on ceramic tiles contaminated with E. coli. Her results revealed bad news for clumsy snackers: The munchies picked up the bacteria within the five-second window. Clark's quirky experiment inspired other food researchers to further investigate the matter. One such scientist, Dr. Paul L. Dawson of Clemson University, showed that food actually follows a "zero-second rule," meaning that bacteria such as salmonella transfer onto food instantly upon contact.
Thankfully, the news isn't as dire as it sounds. In a follow-up set of experiments, Clarke tested the bacteria levels of the university's floors. Her team found very little contamination, even in the most highly trafficked areas of campus. As it turns out, most floors at the University of Illinois are so clean you can eat off of them.
5. $435: The price that humiliated the Pentagon
Back in the 1980s, there was one simple way to win any argument about wasteful government spending -- just bring up the Pentagon's infamous $435 hammer. The absurdly priced tool, which made headlines in 1983 following the publication of a federal spending report, became a popular symbol of government excess.
The truth, however, is more complicated. Sure, there were invoices that showed the Pentagon shelling out $435 a piece for hammers, but the documents were more of a testament to the government's odd accounting practices than its wastefulness. Per Pentagon accounting rules, defense contractors were expected to spread their overhead costs evenly across products to simplify bookkeeping. As a result, massive expenses for things such as research and development and factory maintenance were averaged into the costs of everyday office supplies. That meant that while super-expensive items such as missiles came in cheaper on the register, the price of small-ticket items such as hammers were distorted in the other direction. And because "Pentagon Gets Real Bargain on Missile!" makes a lousy headline, the media latched on to the $435 hammer story.
Since then, the Pentagon has changed its accounting rules, but it's still trying to live down the urban legend about the costly tools lurking in its overpriced toolbox.
6. 100 proof: The measurement that gets you drunk
Proof labels on alcohol bottles were born from the needs of sailors, who wanted assurances about the quality of their booze at sea. Beginning in 1731, members of the British Royal Navy were given an alcohol ration of half a pint of rum per day. (That practice continued, albeit with reduced quantities, until 1970.)
The men loved their rum, but they often became suspicious that their superiors were watering down the goods. To test the rum's potency, sailors would douse a small pile of gunpowder with the liquor and attempt to set it on fire. If the powder lit instantly, the sailors took it as "proof" that the rum was strong enough. But if the powder fizzled, the booze was deemed unfit to drink. Because spirits need to be at least 57.06 percent alcohol to combust, that threshold became known as "100 degrees proof."
The British system eventually made it across The Pond, where Americans simplified the idea by redefining "proof" as twice the percentage of alcohol by volume. Sure, it's not as visually impressive as the sailors' method, but it beats having to take a handful of gunpowder into a bar with you.
7. 1 in 195,249,054: Your Odds of Living on Easy Street
No matter how lucky you’re feeling, your odds of hitting the jackpot in the multi-state Powerball lottery are a don’t-spend-the-money 1 in 195 million. For perspective, your odds of being struck by lightning twice are much more reasonable, at 1 in 39 million.
Still, there are a few justifications for plunking down your hard-earned cash and crossing your fingers. For one thing, it puts you in terrific historical company. When the London Company had to scrape together funding for the Virginia colony in 1612, King James I authorized lotteries to raise capital. More than 150 years later, founding fathers Benjamin Franklin and George Washington ran lotteries to help finance the Revolutionary War and fund new infrastructure. The odds of winning weren’t great, but they beat taxation without representation.
Of course, as long as there’s been a lottery, there have been scoundrels trying to game the system. For the Powerball, cornering the market on the nearly 200 million potential combinations would be logistically impossible and risky. But that doesn’t mean smaller lotteries aren’t susceptible. In 1992, an accountant named Stefan Klincewicz put together a 28-person syndicate to buy up all 1.94 million potential combinations for the Irish lottery. Although lottery officials sniffed out the scheme and put a halt on ticket sales the day before the drawing, Klincewicz and his associates managed to snap up 80 percent of the available tickets. They walked away with roughly $1.8 million USD in winnings, and even though the crew had to split the loot and deduct expenses, they each turned a modest profit.
8. 6,894,200,000 people? The population we can't pin down
During the past century, we've really kicked our world-populating into high gear. In 1950, there were around 2.5 billion of us. Now that number is closer to 7 billion. How close? That's a question that plagues even the smartest thinkers. In order to know how many of us there will be in the future (and where to allocate program dollars to make sure those future folks are happy and healthy), we need to know how many of us there are right now.
Unfortunately, answering that question isn't as simple as lining up everyone for a head count. World-population estimates at any given moment are drawn from data collected in national censuses, but a country's census numbers might be several years old. Demographers can use that data to estimate current populations, but those calculations require assumptions about things like mortality, fertility, and migration rates. Additionally, a nation's census data isn't absolutely accurate even when it's fresh. The Chinese census, for instance, boasts a margin of error lower than two percent. That sounds great, until you realize that the discrepancy could represent as many as 27 million people -- or roughly one-and-a-half New York City metro areas -- who may or may not be living somewhere in China.
But none of these shortcomings stop groups from making bold proclamations. In October 12, 1999, the UN Population Fund symbolically named Bosnian baby Adnan Nevic the world's 6 billionth person. The U.S. Census Bureau snapped back, stating that Baby No. 6 Billion had probably been born four months earlier. Congrats to little Adnan's parents, though!
Thanks to all the assumptions required, future projections can vary wildly. In the past decade alone, UN demographers have estimated that the population will peak at 12 billion this century, only to later revise the estimate to 9 billion. With fluctuations like that, it's difficult to know what sort of population boom we should be bracing for.
9. The Dow at 14,165: The statistic that measures the health of our economy
Most Americans think of the Dow Jones Industrial Average as the canary of our financial coal mine. But what did it really mean when the Dow hit its record high of 14,165 in October 2007?
To answer that, you have to go back to Charles Dow, legendary newspaper mogul and co-founder of The Wall Street Journal. In 1896, Dow created the first version of the Dow Jones Industrial Average. The idea was to monitor the health of the business sector by tracking the performance of the country's 12 largest firms. The Dow was originally measured in dollars, and calculating it was a breeze; accountants just averaged the 12 stock prices. The first Industrial Average on record was $40.94. When the firms were doing well, that average went up; when they performed poorly, the Dow went down.
The measuring system has become more sophisticated over the years. The modern index includes 30 companies, and the Dow has to account for things like stock splits and spinoffs. Thanks to these adjustments, the Dow is now measured in points rather than dollars. A single dollar increase in any of its current members' share prices causes the Dow to rise by about seven points.
So, how does a company get into the Dow 30? It's a bit like rushing a financial fraternity. A three-person committee (which includes the managing editor of The Wall Street Journal) handpicks the companies, looking for stocks with strong reputations, solid growth, and interest from a broad pool of investors. Of the original 12 companies selected, only General Electric is still in the pool. In fact, the "industrial" in the average's name is a bit of a relic. The current incarnation of the Dow includes non-industrial companies such as American Express and The Home Depot. Still, by telling us how the biggest and most stable American companies are doing, the Dow remains one of the best indicators of the overall health of the U.S. economy.
10. 3.14159265 ...: The number that makes us all a little irrational
As the ratio of a circle's circumference to its diameter, pi is a mathematical constant. As an irrational number comprised of digits that will never repeat or terminate, pi is a constant source of amusement for math nerds of all stripes.
Computer programmers have even spent ridiculous amounts of time calculating pi out to its five trillionth decimal place (which is a 2, for the record).
If calculating decimal places isn't your idea of fun, you can always memorize them. The current unofficial world record belongs to Japan's Akira Haraguchi, who rattled off 100,000 decimal places in 2006. People who need help remembering digits often fall back on memorizing a "piem," a poem in which the number of letters in each word corresponds to pi's digits.
American mathematician Mike Keith's 2010 book Not a Wake (that's 3-1-4 letters, if you're counting at home) extends this exercise to 10,000 digits. If you start memorizing now, you'll be ready for next year's Pi Day, on March 14.
This article originally appeared in mental_floss magazine. If it put you in a subscribing mood, here are the details. Got an iPad or another tablet device? We also offer digital subscriptions through Zinio.