# Sine Us Up: It's Square Root Day.

Before today, 4/4/2016, we hadn't had a Square Root Day to celebrate since 3/3/09. Taphouse Studios/Getty

Happy Square Root Day, people! You've probably already been celebrating wildly by planting plants in boxes to make their visible roots grow in a square shape.

Or by taking to the dance floor to do-si-do your partner in a rambunctious square dance. Or by getting ready to watch the Final Four.

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You have to wonder what the folks at Squarespace are up to today. Is it an official company holiday? Are they eating a square meal or getting a square deal? Checking in on Foursquare?

For those who are still wrapping their heads around what we're talking about, April 4, 2016, is Square Root Day because the square root of 16 is 4 (Get it? 4/4/16)? This unofficial holiday won't come around for another nine years (5/5/2025). You could celebrate by brushing up on your square roots. How high can you square numbers without cheating and plugging them into the calculator on your phone? (Thirteen's my mediocre high.)

And what about figuring out the square root of a random number? Can you do that? It's easy enough to figure out the square root of 400, say. But what about the square root of 7,777? You're probably better at figuring out the answer than you might think. (Or maybe you're awesome at this already, in which case, congrats.)

If you know that 8 x 8 = 64 and 9 x 9 = 81, then you know that the square root of 7,777 is between 80 and 90. Splitting the difference between 6,400 and 8,100 means that 85 is going to be the square root of 7,350 about (it's actually 85.7). And from there you can just ballpark it. My guess would be 87. It's 88.1. Not bad. Now you try it. And while you're at it, have fun on this unofficial holiday.