15 Massive Online Databases You Should Know About

massive-online-databases

Think of your favorite open databases. I’m sure Wikipedia and IMDb instantly spring to mind, but you might not be in the need of all that knowledge ever, or a comprehensive database of all things entertainment. Sometimes you need a bit of VLDB (Very Large Data Base) flavor. Something to spice up your data analysis. Something to put the “big” in your big data. Whelp, good person, you’re in the right place. Here are 15 massive online databases you can access and analyze for free, or just peruse at your leisure. 1000 Genomes The 2003 completion of the Human Genome Project…

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15 Massive Online Databases You Should Know About

The DIY Loft Bed Workspace

The DIY Loft Bed Workspace

Bed-and-desk combos are great for students or anyone else short on space. Today’s featured workspace is an impressive DIY project combining a spacious place to work and room to nap or turn in for the night.

Flickr user Bartek Woltanski designed the bed with desk and drawers in SketchUp and then put everything together. The light wood color stands out nicely against the dark wall. We’ve seen similar projects before, but this one is especially impressive as Woltanski’s first woodworking project.

If you have a workspace of your own to show off, throw the pictures on your Flickr account and add it to the Lifehacker Workspace Show and Tell Pool. Include some details about your setup and why it works for you, and you just might see it featured on the front page of Lifehacker.

Student DIY Workspace | Flickr


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The DIY Loft Bed Workspace

How’s That Standing Desk Working Out for You?

How’s That Standing Desk Working Out for You?

Some of us have switched to standing or walking desks to avoid the possible damaging effects of sitting all day. But these desks may not be a cure-all, for a few reasons.

First, even if people who sit all day are less healthy, that may not mean that a standing or walking desk will improve your health. A few experts weighed in with skepticism in a Boston Globe article:

“Standing all day isn’t the answer,” said Alan Hedge, a design and ergonomics professor at Cornell University. “That’s where we were 100 years ago, and we needed to develop chairs to prevent curvature of the spine, backaches, and varicose veins.”

While standing still burns a few more calories as our hearts work harder to circulate blood upward, it also puts more strain on our veins, backs, and joints, especially if we’re overweight.

“Studies haven’t yet determined how much standing helps healthwise,” said Dr. I-Min Lee, an associate epidemiologist at Brigham and Women’s Hospital who has studied the risks of sedentary behavior. In population studies, researchers haven’t been able to determine whether the health benefits of reduced sitting time stem from moving around more or from standing still. And results on whether exercise reduces the health risks of sitting are conflicting.

Another hiccup may come when you look at the effects of walking while working, not on your body, but on your work. A small study published in PLOS One found that people at treadmill desks fared worse on tests of learning, attention, and typing. The subjects weren’t accustomed to working on a treadmill, though, so the effects may be temporary.

When I tried a standing desk, I found it was harder to think. Then again, perhaps I should have tried it for more than ten minutes.

If you’ve tried a non-sitting desk, how did it work out for you? Was there a difficult transition period, and how long did it take to get over it? Definitely tell us how long you’ve been happily using the desk, or if you quit, tell us why!

Photo by Kiran Jonnalagadda.


Vitals is a new blog from Lifehacker all about health and fitness. Follow us on Twitter here.


via Lifehacker
How’s That Standing Desk Working Out for You?

Blink Blink: Creative Circuits Designed by Girls, for Girls

Girls using a blink blink circuit kit.From ambitious entrepreneurs to casual meet-up participants, women are proactive about engaging with STEM and with other women in their field. Besides their shared affinity with science, tech, engineering, and math, they often find that they have another thing in common. Many of these women can recall a time when […]

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The post Blink Blink: Creative Circuits Designed by Girls, for Girls appeared first on Make: DIY Projects, How-Tos, Electronics, Crafts and Ideas for Makers.


via Make: DIY Projects, How-Tos, Electronics, Crafts and Ideas for Makers
Blink Blink: Creative Circuits Designed by Girls, for Girls

Reporting Net Neutrality Violations Is Now A Snap… Actually Identifying Them Not So Much

As you might have heard, the FCC’s new net neutrality rules went live on Friday and, contrary to ISP and friend prognostications, the internet did not explode into a fiery cacophony of Armageddon-esque proportions (surely that happens later). With the courts refusing a stay of the rules, the FCC’s neutrality protections will remain intact until either the ISPs are victorious in court, or there’s a 2016 party (and associated FCC leadership) shift. Until then, consumers can file their complaints with the FCC in a variety of ways, including snail mail.

Of course, actually determining whether your ISP is up to no good is another issue entirely, and unfortunately for those of you sick-to-death of the neutrality discussion, getting the rules in place is really just the beginning.

We’ve talked a few times over the years about people crying net neutrality wolf, and attributing perfectly run-of-the-mill network issues to malicious intent. That’s sure to be an even bigger problem going forward. The average internet user doesn’t really have the ability to differentiate run-of-the-mill routing or DNS problems from aggressive anti-competitive behavior, and in the new age of more subtle net neutrality infractions, that’s probably going to be more true than ever. That’s of course why folks like MLAB have started offering an internet health test that will investigate your connection for hints of ISP skulduggery.

If you’ve yet to run the test, you might want to; data’s going to be stored, cataloged, and eventually publicized for potential use against neutrality violators:

"An individual test may be considered an aberration," (Free Press boss Tim) Karr wrote. "In order to make the case that there’s systemic throttling or degrading you need to perform several tests from different addresses and at different times. That’s what we’re hoping to show by gathering data from hundreds of thousands of separate tests." "I think participating in the Internet Health Test is the best thing an Internet user can do to gather comprehensive evidence of abuse," he added. Battle for the Net hasn’t published the results of its analysis on Internet Health Test data yet, but it plans on doing so sometime in the future."

So while companies and organizations like MLAB should be able to substantiate neutrality violation claims with hard data, that’s going to be notably less likely for individual consumers. The problem, as we’ve touched on previously, is there are still a variety of ways to violate net neutrality while looking like you’re just engaging in everyday business affairs from a network analysis perspective. For example, there’s every indication that the FCC is going to let zero-rating and cap-related shenanigans like AT&T’s Sponsored Data and T-Mobile’s Music Freedom continue as is.

As Facebook and Google are painfully learning overseas, most neutrality advocates realize these kinds of zero-rated programs violate neutrality by tilting the playing field against smaller companies or independent operations — all while convincing users they’re doing them a favor. So ISPs certainly can get away with neutrality violations under this new paradigm — they just have to be much more clever about it while massaging public sentiment. Whether the FCC cracks down on zero-rating (the practice of letting some companies buy their way around already arbitrary usage caps) should provide a pretty good litmus test for whether or not the FCC’s going to be willing to go the extra mile on enforcement.

Of course, if nobody files complaints, ISPs will be sure to insist that this is proof positive that there was never anything to worry about in the first place. Except that’s not true: the absence of complaints could indicate the threat of the rules is working as intended. In fact, we’ve already seen transit and last mile ISPs suddenly and magically get along beautifully after a year of very ugly bickering, thanks simply to the mere threat of real rules.

All of that said, we’re still in a much better place than we were under the original 2010 rules, which excluded wireless and had enough loopholes to drive entire military convoys through. Of course, if you’re still the type to buy into the ISP (and paid friend) narrative that meaningful Title II-based net neutrality protections will destroy the internet, crush free speech, hinder innovation and harm puppies, then there’s probably no evidence on earth that’s going to knock you off that particular perch. But while you’re busy waiting for the internet to die to make a political point, the rest of us will need to remain vigilant to ensure that the FCC, now equipped with the right tools, actually does its job.

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Reporting Net Neutrality Violations Is Now A Snap… Actually Identifying Them Not So Much

Giving A Truck A Camera And A TV Is The Best Idea We Never Thought Of

Giving A Truck A Camera And A TV Is The Best Idea We Never Thought Of

Alright, ignore that this is a terrible ad from Samsung, a massive South Korean multinational conglomerate that also dabbles in surveillance and weapons technology, for a second and just BASK IN THE GENIUS. Mostly because it seems like one of those brilliant ideas that everyone should’ve thought of before but didn’t.

If you’ve ever been stuck behind a truck on a narrow two-lane road before, you know how annoying that can be. The truck is slow as hell, and you want to pass it. Only thing is you can’t, because the truck is so enormous that you can’t see if there’s another equally massive truck heading the other way, ready to crush your face into an unrolled blintz the second you pull out to pass.

Normally, you either risk it because you’re a maniac like us, or you just sit there and let your blood pressure rise for a little while.

But Samsung’s Argentina branch saw this sort of thing, and saw that it was Bad. So to make it Good, they just hooked up a camera to the front of a truck, and then a whole bunch of TVs to the back of the truck. The TVs on the back display what’s going on in front, so you can see if your face will or will not indeed become blintzified once you try to pass.

It’s absurdly simple, really, when you consider that the sort of technology to make this happen has been around for over a decade now.

Alas, it’s also painfully obvious why it’s almost certain you’ll never see it on actual roads. Truckers and trucking companies can operate on some pretty tight margins, and the added cost of fitting the system to a truck, plus the price of fuel lost due to the added weight, virtually guarantees no company would ever go for it.

We can, however, dream.


Contact the author at ballaban@jalopnik.com.
Public PGP key
PGP fingerprint: 0D03 F37B 4C96 021E 4292 7B12 E080 0D0B 5968 F14E

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Giving A Truck A Camera And A TV Is The Best Idea We Never Thought Of

Bug-Proof Your Home Like A Pro

Bug-Proof Your Home Like A Pro

Imagine a future without bugs! Sure, some learned ecologist will probably claim that these eerie tentacled creatures potter around at the bottom of the ecosystem doing important work in the grand scheme of things, but a wholesale elimination of the cockroaches and the mosquitos and the bed bugs of the world is clearly a grand and worthy goal. Unfortunately, stubborn old mother nature refuses to let it happen and I suspect it’s not going to be any sort of a topic at the next election. So with the cold, crystalline days of bug-free winter giving way to the insect-friendly sweatbox that is summer, here’s how to do the next best thing beyond making an entire species extinct—banish them from your apartment.

The Philosophy

If a man’s home is his castle, then you want to think of your apartment as an air-tight, hermetically-sealed bunker. I learned this from an exterminator I used to hire to check out and bug-proof an apartment before I moved into it. (Yes, I am that paranoid and weirded out by the scuttling beasts.) He seemed to have good credentials and know what he was doing—even if a large part of each visit involved telling anecdotes about Rachel Ray’s New Jersey abode and her ongoing mouse problem (a situation exacerbated by her no-kill stance towards any and all creatures except the ones she cooks). The main tactic was always to stop any wandering bugs from entering the apartment from adjoining units or outside. The thinking goes that you can’t really do much about the hoarder downstairs or the empty pizza box collector next door, so you want to create an impenetrable barrier between their slovenly habits and a calm and peaceful enjoyment of your home.

Holes In The Wall

First up, whether you live in a fancy new building or a decrepit old co-op, there’s a good chance that whoever installed your stove and fridge half-assed the job. So pull out your appliances—very slowly and very carefully, especially if a gas connection is involved—and check out the spots where the pipes and plugs go into the wall. Now marvel at the sort of gaping hole a middle-class family of possums could strut through. The majority of any bug-related visitors to your abode are likely coming through this gateway, so you’ll want to close this off pronto.

Don’t worry if your DIY skills are lamentable—this is a cinch. Pick up some caulk, some gauze stuff (that sort of looks like a bandage), some steel wool and some gloves from a hardware store. This stuff is all cheap and you should be looking at change from a $20. Perhaps grab a six pack too, as a preemptive pat-on-the-back for the good work you’re about to do. Now depending on the size of the hole, you may want to insert some steel wool into it to act as an extra barrier to bugs. You might have a tool to do this, but a butter knife also works just fine. (Also, it might seem counterintuitive, but buy the thicker steel ewool rather than the thinner and more tightly-wound stuff—determined roaches have been known to successfully eat through the thin threads, whereas the thicker wool will hopefully cut ‘em up good and proper on the inside should they attempt to chow down on it.) Ed Note: Steel wool is highly flammable! Use only in holes that are far away from gas lines, ovens, and heat!

Once you’ve stuffed the hole with steel wool, cut some of the gauze to the right size and stick it over the hole. Now you’ll want to caulk over the gauze, hopefully creating a permanent barrier. You can buy little plastic spatula things for this, but most times it’s easier (and neater) to use your finger and a paper towel. Smooth it out, clean up any errant bits of caulk with a wet paper towel, then admire your handiwork while also being thoroughly grossed-out when you realize how much rotting food the last person left under the stove.

Water Works

Once you’ve dealt with the offending stove and fridge, you’ll want to take a similar approach to the pipes under the kitchen sink and the bathroom facilities. Ideally, the holes around them should already be plugged up—possibly with that expanding foamy stuff—but again there’s a chance they’re not. So get busy with your newly acquired caulking skills again.

Contrary to popular scare stories about bugs living in boxes of opened cereal, most of them aren’t actually after your food as much as water and a moist environment. Plumbing pipes are like freeways to them, and a dripping tap is an oasis on a dingy horizon. Destroy this world.

The Original Nooks And Crannies

With the main holes in your apartment now fixed, it’s time to take a good look around at the rest of the unit and spot any other potential entrances. Are there sizable holes in the closets, often along the floor? What about under the baseboards? Do your outlets or light switches have gaps around them leading directly into the wall? What about any heating or radiator pipes? All of these things should be taken care of—again using your steel wool and caulk arsenal as appropriate.

If you really want to mollycoddle your bug paranoia, you can also buy those plastic outlet covers that are meant for babies and plug up another hypothetical entrance. Although the one time I tried them they were near impossible to get back off. Your call.

Doors And Windows

Next, you’ll want to fortify your lovely windows and doors for any inquisitive bugs who might consider intruding on your peace and quiet that way. Check out how tightly your front door actually closes—a flashlight can help you identify any gaps along the top and bottom of it—especially if it leads to a dirty communal hallway. Measure the gap and pick up a weather strip in the appropriate size from a hardware store. These things require little more installation than peeling off a strip of backing paper and sticking the rubber or foam to the bottom of the door. (This will also help keep your apartment cool or warm, depending on the season.)

When it comes to your windows, first check to see if they actually close—or are there gaps at the top or bottom where they’ve either been fitted badly or deteriorated? Again, you’ll want to seal up the gaps using a foam weather strip—cut it to size and stick it on.

Next, check the condition of the screens. Run your fingers across them (or use a flashlight if it’s getting dusky) and identify any holes. Tears and breeches can be quickly fixed with some of that replacement screen mesh—just cut it to size and apply—although a piece of tape will also do in a pinch.

Most flying bugs should now be kept out, but if you happen to live in a place where summer means battling blood-thirsty mosquitos, you might also want to pick up a bunch of cheap adjustable screens from a dollar store and double up on your protection. Although in my experience one of those buzzing malaria menaces will still somehow manage to get through the barricade. At which point you’ll just want to hope that your significant other finds it endearing when you and the cat are attempting to track down an infernal mosquito at 3 a.m. using nothing more than the flashlight on your iPhone.

Get A Cat

Speaking of which—and with every intent of laboring the point—get a cat. These animals have special noses created by science that allow them to sniff out bugs long before you’ve caught sight of them. Also, there’s some sort of olfactory honor system that goes on in the animal world: Bug or mouse or other critter considers entering your domain, catches a whiff of the feline, and decides to pass. It’s a good arrangement. I once knew someone whose Brooklyn apartment was besieged by a squirrel. Their landlord offered to lend them his two cats for a couple of days. Despite sounding like a half-assed solution, they never saw the squirrel again.

Next To Godliness

At this point, you should have a largely non-porous apartment. But that doesn’t mean you should drop your guard in the war against the creepy crawlies. Assuming there’s a general level of cleanliness going on in your place, there are also a couple of simple updates you should consider. Most importantly, get a small garbage can with a lid that closes. The Simple Human brand makes a brushed stainless steel can that costs about $20 and is pretty much perfect as far as these things go. It seals tight and you can use plastic bags from the supermarket it in. Remember: Taking the trash out daily is not hardship.

Also, don’t leave a bunch of unwashed recycling bottles out in a bag on the floor. Stick ‘em in the freezer if need be until it’s recycling day. Roaches, in particular, will seek out a beery smell, although it’s unsure which side of the great IPA debate they come down on.

Finally, try and minimize your clutter. Not because it attracts bugs or pests per se, but because it offers a hiding place. Piles of paperwork, print media, or other assorted junk are not cool. Mosey on over to the Container Store and buy some storage. It’s kinda cool and it’ll also make your next eventual apartment move easier.

Poisons And Miscellaneous Natural Remedies

You can read a lot about natural miracle cures for certain bugs on the Internet, but don’t put all your hopes and fears into them. A peppermint plant will not really repel ants. Rubbing cider vinegar on your skin is not really going to keep the mosquitos away—you’re just gonna walk around with a tart apple-ish whiff. (Although I am prepared to believe that the old bartender’s tale of tonic water as a mosquito repellent works.) So sure, try them if you want, but the best solution is to eliminate the point of entry. Diatomaceous earth is often touted as a natural way to get rid of roaches; I’ve viewed apartments where the current tenant has placed a perimeter line of the stuff around a stove, but why not just sort out the source? It’s a classic prevention over cure situation.

Also, I’ve been told by more than one pest control professional that most baits and traps you can buy in supermarkets are largely ineffective: By the time the poisons have been approved for commercial sale, they’ve been used by the pros for a number of years and bugs have often built up an immunity to them. I’m no conspiracy theorist, but it sounds like there’s some sense in that. Just like it seems that most times a spritz with any old kitchen cleaner is just as effective as a blast of Raid on something. Although definitely remember to clean up after you’ve notched up a kill, lest that horror story about a bug leaving behind microscopic eggs comes true.

Do Your Research

While no apartment can be guaranteed completely bug-free, when you’re moving or between places there are some simple steps you should take. First, check the Bed Bug Registry website (http://ift.tt/M37qZP) to see if anyone in the building—or even next door—has reported a problem with bed bugs.

Likewise, before signing a lease, ask your landlord about the building’s history with said devilish critters. In some states (like New York) they have a duty to disclose any issues. This may or may not be a total deal-breaker for you—unfortunately, in a large communal building some fuckwit is always going to bring in some rickety infested furniture someone has dumped because, you know, they think that’s what people in Brooklyn do and isn’t it so great there’s all this free stuff by the curb. Seriously, I once interviewed an upcoming rapper from the west coast who was living in Bushwick for the summer and seemed overjoyed that she’d found a mattress outside on the street that she could drag into her sublet and sleep on for free. So, yeah, ask a potential landlord about bed bugs, if only to judge their response and gauge how they might react should an issue come up.

Secondly, unless you are at one with the six- and eight-legged beauties of the animal kingdom, do not live in a basement. No matter how many of the above precautions you take, you’re still basically ground zero for bugs. I once lived in a finished half-basement—not even real subterranean dwelling!—and took a turn for the crazy trying to fathom where some ants were coming in from. I considered leaving a video camera pointed at the wall all night. It turned out the diligent, hard-working proles had managed to burrow a small tunnel through the wall and out of some exposed brick.

Lastly…

Your biggest ally in the march against bugs is your sanity. It is very easy to get caught up in a sleepless cycle caused by worrying over bugs. Trust me: Never research bugs on the Internet at night. You’ll simply come across bat-crap crazy horror stories, disgusting images that will become burned in your subconscious, and people claiming that if you see one intruding creepy crawly it automatically means there are eight gazillion of them hiding just out of sight. Instead, try and stay calm and remember the golden rule—no bug has yet managed to successfully defeat a good old-fashioned foot stomp.


Phillip Mlynar lives in Queens, NYC. When not writing about rappers for Red Bull, NYLON, and the Village Voice, he muses on the feline form for Catster. His Twitter claims he’s the world’s foremost expert on rappers’ cats.

Illustration by Tara Jacoby.

Adequate Man is Deadspin’s new self-improvement blog, dedicated to making you just good enough at everything. Suggestions for future topics are welcome below.


via Lifehacker
Bug-Proof Your Home Like A Pro

How NYPD Badges are Made

With any luck, you’ll never see a police badge up close. And even if one is flashed in your face, afterwards as you’re sitting on the curb wearing zip-ties you probably won’t be thinking "Gee, I wonder how those badges are made."

But for those who are curious, a Brooklyn-based company called United Insignia has a video up showing the process. We always assumed the NYPD’s "shields" just came out of a stamping machine, but there’s actually a fair bit of handwork involved:

According to the NYPD quoted here, the current design dates back to 1902. Here’s their description of the production process:

Our modern shield is made of nickel silver. It is first die-struck in a drop hammer which gives it impression and then is pounded until the desired height of the characters is reached. The perimeter is then blanked and embossed and the numbers and lugs are hard soldered. The badge is then dipped, cleaned, nickel-plated and polished to a high gloss.

If you want to see what some other cities’ cop badges look like, check out our older post on the subject.

Via Herman Yung


via Core77
How NYPD Badges are Made

These Math Secrets Will Make You Love Times Tables

These Math Secrets Will Make You Love Times Tables

Most people will probably remember the times tables from primary school quizzes. There might be patterns in some of them (the simple doubling of the 2 times table) but others you just learnt by rote. And it was never quite clear just why it was necessary to know what 7 x 9 is off the top of your head.

Well, have no fear, there will be no number quizzes here. Instead, I want to show you a way to build numbers that gives them some structure, and how multiplication uses that structure.

Understanding multiplication

Multiplication simply gives you the area of a rectangle, if you know the lengths of the sides. Pick any square in the grid, (for example, let’s pick the 7th entry in the 5th row) and colour a rectangle from that square to the top left corner.

These Math Secrets Will Make You Love Times Tables

A rectangle of size 5 × 7 in the multiplication table.

This rectangle has length 7 and height 5, and the area (the number of green squares) is found in the blue circle in the bottom right corner! This is true no matter which pair of numbers in the grid you pick.

Now let’s take this rectangle and flip it around the main diagonal (the red dotted line).

These Math Secrets Will Make You Love Times Tables


The same rectangle, flipped.

The length and height of the rectangle have swapped, but the area hasn’t changed. So from this we can see that 5 × 7 is the same as 7 × 5. This holds true for any pair of numbers — in mathematics we say that multiplication is commutative.

But this fact means that there is a symmetry in the multiplication table. The numbers above the diagonal line are like a mirror image of the numbers below the line.

So if your aim is to memorise the table, you really only need to memorise about half of it.

The building blocks of numbers

To go further with multiplication we first need to do some dividing. Remember that dividing a number just means breaking it into pieces of equal size.

12 ÷ 3 = 4

This means 12 can be broken into 3 pieces, each of size 4.

Since 3 and 4 are both whole numbers, they are called factors of 12, and 12 is said to be divisible by 3 and by 4. If a number is only divisible by itself and 1, it is called a prime number.

But there’s more than one way to write 12 as a product of two numbers:

12 × 1

6 × 2

4 × 3

3 × 4

2 × 6

1 × 12

In fact, we can see this if we look at the multiplication table.

These Math Secrets Will Make You Love Times Tables

The occurrences of 12 in the multiplication table.

The number of coloured squares in this picture tells you there are six ways you can make a rectangle of area 12 with whole number side lengths. So it’s also the number of ways you can write 12 as a product of two numbers.

Incidentally, you might have noticed that the coloured squares seem to form a smooth curve — they do! The curve joining the squares is known as a hyperbola, given by the equation a × b = 12, where ‘a’ and ‘b’ are not necessarily whole numbers.

Let’s look again at the list of products above that are equal to 12. Every number listed there is a factor of 12. What if we look at factors of factors? Any factor that is not prime (except for 1) can be split into further factors, for example

12 = 6 × 2 = (2 × 3) × 2

12 = 4 × 3 = (2 × 2) × 3

No matter how we do it, when we split the factors until we’re left only with primes, we always end up with two 2’s and one 3.

This product

2 × 2 × 3

is called the prime decomposition of 12 and is unique to that number. There is only one way to write a number as a product of primes, and each product of primes gives a different number. In mathematics this is known as the Fundamental Theorem of Arithmetic.

The prime decomposition tells us important things about a number, in a very condensed way.

For example, from the prime decomposition 12 = 2 × 2 × 3, we can see immediately that 12 is divisible by 2 and 3, and not by any other prime (such as 5 or 7). We can also see that it’s divisible by the product of any choice of two 2’s and one 3 that you want to pick.

Furthermore, any multiple of 12 will also be divisible by the same numbers. Consider 11 x 12 = 132. This result is also divisible by 1, 2, 3, 4, 6 and 12, just like 12. Multiplying each of these with the factor of 11, we find that 132 is also divisible by 11, 22, 33, 44, 66 and 132.

It’s also easy to see if a number is the square of another number: In that case there must be an even number of each prime factor. For example, 36 = 2 × 2 × 3 × 3, so it’s the square of 2 × 3 = 6.

The prime decomposition can also make multiplication easier. If you don’t know the answer to 11 × 12, then knowing the prime decomposition of 12 means you can work through the multiplication step by step.

11 x 12

= 11 x 2 × 2 × 3

= ((11 x 2) × 2) × 3

= (22 × 2) × 3

= 44 × 3

= 132

If the primes of the decomposition are small enough (say 2, 3 or 5), multiplication is nice and easy, if a bit paper-consuming. Thus multiplying by 4 (= 2 x 2), 6 (= 2 x 3), 8 (= 2 x 2 x 2), or 9 (= 3 x 3) doesn’t need to be a daunting task!

For example, if you can’t remember the 9 times table, it doesn’t matter as long as you can multiply by 3 twice. (However this method doesn’t help with multiplying by larger primes, here new methods are required – if you haven’t seen the trick for the 11 times tables watch this video).

So the ability to break numbers into their prime factors can make complicated multiplications much simpler, and it’s even more useful for bigger numbers.

For example, the prime decomposition of 756 is 2 x 2 x 3 x 3 x 3 x 7, so multiplying by 756 simply means multiplying by each of these relatively small primes. (Of course, finding the prime decomposition of a large number is usually very difficult, so it’s only useful if you already know what the decomposition is.)

But more than this, prime decompositions give fundamental information about numbers. This information is widely useful in mathematics and other fields such as cryptography and internet security. It also leads to some surprising patterns – to see this, try colouring all multiples of 12 in the times table and see what happens. I’ll leave that for homework.

Anita Ponsaing is Research Associate in Mathematics at University of Melbourne.

This article was originally published on The Conversation. Read the original article. Image by Tiger Pixel under Creative Commons license.

via Gizmodo
These Math Secrets Will Make You Love Times Tables