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10 Number Facts You’ll Wish You Knew Sooner

Ever wonder why February has 28 days or bank PINs have four digits?

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Eleven and twelve

Why not oneteen and twoteen? The reason behind the shift in number naming is that eleven comes from the Germanic term ainlif, which translates to “one left,” or in this case, “one left over” after you count out ten of something. Twelve follows the same rule. It comes from twalif—“two left.” Why we switched from lif to teen (which itself means “ten more than”) for 13 through 19 is something that is sadly lost to antiquity. Learn more about why 11 and 12 aren’t part of the “teens.”

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2,000 calories a day

This number wasn’t plucked out of thin air—the FDA based this suggestion on science. The average person requires about 2,350 calories a day, according to a U.S. Department of Agriculture survey. But there’s a big caveat: That word average could encourage plenty of people to overeat. Most women need fewer calories than men do, and some older women need as few as 1,600 a day. In establishing the final rule in 1993, the FDA noted that “2,000 calories is easier to use in quick, mental calculations compared to other calorie levels such as 1,900 or 2,350 calories.” So it rounded down to 2,000, a good middle ground for our disparate calorie needs. Here’s exactly how to calculate the number of calories you, specifically, need a day.

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911 for emergency calls

Early phone systems didn’t employ phone numbers—the operator had to connect your call manually—and this precluded the real need for a universal emergency code. But when phone numbers became the norm, that changed, and in 1967, a presidential commission urged the creation of a nationwide solution. AT&T, which operated most of the telecoms at the time, chose 911 because it was available and very easy to remember and could be quickly dialed on rotary phones. Check out some other fun and surprising trivia facts about pretty much everything.

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55 miles per hour

What is the reason behind this common speed limit? Gasoline consumption. In 1974, in response to the worldwide oil crisis the year before, Congress and the Nixon administration signed into law the Emergency Highway Energy Conservation Act. Part of the act mandated that highways across the nation have a speed limit of 55 miles per hour in hopes that the lower speed limit would help reduce high levels of fuel consumption. The law was modified in 1987—allowing for some 65 mph zones—and then ultimately repealed in 1995. Despite the change, there is still debate about whether a 55 mph speed limit is safer than a significantly higher one, especially given the steep advances in automotive technology over the years. Learn why road signs are designed in different shapes.

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5280 feet in a mile

As if imperial units weren’t confusing enough! Why not just go for a clean 5000? Even 5200 feet seems like it would make more sense. Well, we can blame the ancient Romans. Our mile began as an ancient Roman unit of distance called a mille passum, or “a thousand paces.” A “pace,” in ancient Rome, was considered to be the length of five human feet, so a mille passum measured about   Converted into our modern twelve-inch feet, a mille passum measured about 4850 of those. So how did that evolved into the 5280-foot mile?

It wasn’t till 1592 that the British Parliament decided to standardize the length of the mile. They based it off of a unit called the furlong, which was used primarily in agriculture to measure the length of a plowed furrow in a field. A furlong measured 660 feet, and Parliament decided that eight of them–5280 feet total–would officially be a mile. Learn more about the history of the mile.

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26 letters in the alphabet

There are a lot more than 26 sounds in the English language, so why do we only have 26 letters? Well, this wasn’t always the case. Our alphabet has evolved over thousands of years to become the version we’re so familiar with. In just the past few hundred years, our alphabet has lost six letters. Thanks to the transition from Middle English to Modern English, combined with the invention of standardized typography, these letters became obsolete, leaving us with the 26 we have today. Some of the lost letters include the “eth,” which made the “th” sound we hear in “the” or “then”; and the “ethel,” which made the “oi” sound in “coin” or “join.” Linguists, though, assure us that we don’t have to worry about any of the core 26 letters disappearing any time soon. Learn which letter was the last to be added to the alphabet (it wasn’t Z!).

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26.2 miles in a marathon

There’s more to the story than the message delivered by that legendary ancient Greek soldier from the site of a battlefield in Marathon, Greece, to Athens. The modern marathon was born as a flagship event in the first Olympic Games, in 1896, with a distance of approximately 25 miles, targeted to parallel the Marathon-to-Athens mileage. But race organizers for the 1908 Olympic Games in London wanted to add local flair to their course: The race began at scenic Windsor Castle and ended at iconic White City Stadium, with runners finishing only after jaunting around the track toward the royal viewing box. That distance was 26.22 miles, and for the 1924 Games, the organizing body standardized the race length to compare racers over multiple Games. Unfortunately, there were two Games between those years that didn’t use the 26.22-mile standard: In 1912, the race was 24.98 miles, and in 1920, the course was 26.56. These other famous Olympic moments also changed history.

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9 innings in baseball

In the early days of the Great American Pastime, baseball games didn’t have a specified number of innings. In the 1840s, games lasted until any team scored 21 runs. Does that sound like it would take days? Well, this wasn’t the case back then. In fact, games only lasted about six innings, as teams tended to scored run after run. This was because the skill level of the pitchers didn’t match the skill levels that the batters were playing at. Things began to change when pitching became a more important part of the sport and pitchers became more skilled. The tipping point occurred when a game in 1856 had to end in a 12-12 tie when the game ran into the night. A committee gathered later that year to regulate the length of the game, and they decided that each game would have nine innings because that was the number of players per team (which had also been decided very recently).

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28 days in February

One of the first Roman calendars (in early BC) did not measure the winter months; it had only 304 days and ten months (March through December), with six months of 30 days and four of 31 days. According to legend, the second king of Rome tacked on an extra two months (January and February) plus 50 days. To make the new months longer (and possibly to honor a Roman superstitious dread of even numbers), he subtracted one day from the 30-day months, leaving 56 total to divide between January and February (or 28 days each). Superstition won the day again, when January was given an extra day for an uneven 29. February, with an even 28 days, was declared a month of “the infernal gods.” And that’s how it became the shortest month.

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Four-digit PINs

ATMs were created in 1967 by a Scottish man named John Shepherd-Barron, who thought that getting cash should be as easy as getting a chocolate bar. But the difficulties lay in ensuring that you were who you said you were. To prevent problems, Shepherd-Barron developed a special type of paper check that acted as a precursor to the debit cards we have today. Each check would cause his cash machine to request a personal identification number—or PIN—that only the account holder knew. Since Shepherd-Barron already had a six-digit ID number he had memorized, given to him by the army, he was going to make the machine require a six-digit PIN from everyone who used it. That likely would have been the standard, but he was overruled …by his wife. She believed that six digits were two too many to remember, and four became the standard. Next, check out even more surprising trivia facts you’ll wish you knew sooner.

Reader's Digest
Originally Published in Reader's Digest