Why This Viral Math Trick Is Blowing Everyone's Minds

If only they taught this in high school...

woman writing on a whiteboard in math class

Of all the things you learned in math class, percentages were probably the most useful. And yet, most of us still aren't very good at them…which is probably why this nifty trick to make calculating percentages easier on the spot is now going viral. It was shared by self-proclaimed "math whizz" Ben Stephens last week, and it's making everyone wonder why they've never learned this before.

If you're scratching your head wondering what the answer is, it's 3.

Basically, the premise is that a lot of percentages would be easier to figure out if you simply flipped the numbers. For example, if someone asked you on the spot what 18 percent of 50 was, you'd probably ask them why they suddenly decided you were a mathematical genius. But 50 percent of 18 is easy to figure out—and, in both cases, the answer is 9.

the hangover math gif

Needless to say, his tweet quickly went viral, and got people wondering how on earth they never knew this before.

Even people who teach math or hold advanced degrees in the subject were blown away.

Of course, the trick doesn't make all percentages easier to figure out. For example, calculating 43 percent of 87 isn't much easier than calculating 87 percent of 43. (The answer, by the way, is 37.41.) Once you get into the decimals, it's a whole other ball game for anyone who isn't Matt Damon's character in Good Will Hunting.

But, as Ben wrote on Twitter, it's interesting that "pretty much everyone gets that 3 x 5 = 5 x 3 [but] we have never thought (or been taught) to think of calculating a percentage as a multiplication operation." And it's a neat trick to break out next time you're splitting the dinner bill four ways. And for more mind-blowing math, check out these 40 Facts About Numbers That Will Make You Feel Like a Mathematical Genius.

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Diana Bruk
Diana is a senior editor who writes about sex and relationships, modern dating trends, and health and wellness. Read more
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