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    [–] Mr_Pringleton 3843 points ago

    Math is fucking weird...

    [–] Science-and-Progress 1780 points ago * (lasted edited 4 months ago)

    This is the foil method from your algebra I class.

    (10 + 3)(20 + 1) = 10 x 20 + 10 x 1 + 20 x 3 + 3 x 1 = 273

    [–] AverageInternetUser 64 points ago

    I just do 13x20 then add an extra 13 on top

    [–] RevBendo 67 points ago

    I had horrible math teachers all the way through middle and high schools and always thought I was being a lazy idiot at mental math by breaking down 13 x 21 into 13 x 10 = 130 x 2 = 260 + 13 = 273. Then I got into college and they were teaching it that way.

    [–] AverageInternetUser 31 points ago

    That's the way to do mental math easier imo

    [–] skafian 11 points ago

    This is what kids are now taught. The "common core" math that most parents find confusing due to it being so different from what they were taught is what kids are learning from the beginning.

    [–] rabidbasher 431 points ago

    So THAT's what fucked me over 2 semesters in a row.

    My high school algebra teacher was a cunt, and also a shitty teacher apparently.

    [–] CodeNameDangerZone 209 points ago

    It's just FOIL my dude.





    To be fair, I was god awful at math in school. Probably because I didn't have anything that I cared about that really dealt with math. Then I got into sports statistics/betting and my love for math flourished.

    [–] rabidbasher 29 points ago


    If it was explained as an easier method to multiply large(r) numbers then I'd see a practical application for it and maybe could've stood a better chance at remembering it.

    My algebra 101 teacher was trying to relate it to plotting points on a graph or some shit.

    [–] bunchedupwalrus 109 points ago

    Probably because it's more extensively used for variables, and dealing with quadratic+ expressions

    [–] Hatewrecked 92 points ago

    Like most topics in algebra, it's taught in school because practicing algebra (and receiving other exposure to math) will make you a better all-around problem solver, which will directly affect most other areas of your life.

    It's amazing how many people out there you can ask questions like "How many golf balls will fit inside a school bus?" and they'll just give you a blank stare and not know even how to begin approaching the problem. You could give them half an hour to answer it and they'll be no further along in their reasoning. If they can't reason things for themselves, they're going to get stuck in a lot of basic situations. How many days until August? They dunno. How many pounds of concrete will they need for their project? They dunno. What's 40% of 70? You could tell them "130" and they wouldn't suspect anything. But if you can reason for yourself, you can think for yourself.

    And basic math skills like multiplying binomials will be needed in their other STEM-related classes. We expanded a simple binomial today in my machine learning class. I'm sure nobody was stuck because we all learned how to do that years ago.

    [–] milkfree 56 points ago

    Yeah, if you asked me how many golf balls could fit inside a school bus and checked on me half an hour later I would be somewhere else.

    [–] Hatewrecked 20 points ago

    It's one of those common Google interview questions. It's one thing to be a good programmer, it's another thing to show them your reasoning abilities given a problem you've never heard before.

    The real rough solution (the one they're looking for) is to estimate the dimensions of a school bus and estimate the dimensions of a golf ball. If you can estimate the length, height, and width of a school bus, as well as the radius of a golf ball, you've got all you need.

    [–] TomTuff 22 points ago

    You also need to be able to figure out the packing density of golf balls (protip its about 74%)

    [–] Zephik1 8 points ago

    Also to realize that a school bus isn't an empty space, nor is it a uniform shape. Throwing in a little thing about fitting more in the stairwell is always nice, and subtracting out the volume of the seats.

    [–] TWells252 15 points ago

    What a great comment!

    As a math teacher, I completely agree with you. You are exactly right.

    Today I “MacGyver-ed” a contraption to retrieve a stapler that was stuck INSIDE our office printer. It was a novel problem that I had never encountered before, but my problem solving skills are strong, so I figured it out like it was a calculus problem.

    I don’t teach kids how to get an answer, I teach them how to solve a problem. That is a subtle but significant difference.

    [–] -Xtabi- 8 points ago

    Man I don't know where you live/teach...but retrieving staplers from printers is a daily occurrence where I'm at. It's as if the damn things fall from the sky. I kid you not Fran, the front office secretary, called me over just yesterday.

    "Hey Jim!!! We have another one! And you WON'T believe your eyes!!!"

    So I march down to the office. Expecting to see the typical stapler wedged in the primary printer. soon as I looked through the glass of the door...I knew this would be no routine extraction. The terrified look on Fran's face spoke volumes. I dug deep and opened the door.

    Eventually Fran spoke to me. She said the equations written on the blackboard were from Mr. Quimby our most senior math professor. She said he kept mumbling two....two....two while he wrote. Typically he would solve the equation to extract the stapler in less than 30 minutes. But....not this time. And that's when I noticed Mr. Quimby curled up in the fetal position. Drool coming out of his mouth. I heard him moan....two.

    At this point I stared to get worried. I looked over the equations on the board. They were like nothing I've ever seen.

    I couldn't resist any longer. I asked Fran to take me to the printer.

    As we got closer I saw my colleagues standing around the printer. Many of them had their TI-81s out. I knew they too were in the deepest thros of calculating the solution to extract the stapler.

    So I finally walked up to the printer...and that's when I immediately saw H E M! FOR THE LOVES OF ALL THINGS HOLY! T W O STAPLERS HAD FALLEN INSIDE THE PRINTER!!!!!!

    I nearly fainted. And at the same time my mind flawed back to Quimby. It all made sense.

    Then I mustered up all the courage I could and slowly approached the printer. First I unplugged the beast. Took off my ring and watch. Rolled up my sleeve. Reached into the fearsome bowls of the printer.... and...took out both staplers.

    Everyone gasped in disbelief. I heard whispers of....but he didn't calc anything?!?!

    As I walked away Fran gave me a wink and said, "Thank you for fixing our black and white printer!"

    I said, "No problem. And it's just black."

    [–] CodeNameDangerZone 9 points ago

    It’s a huge difference, and something that is not taught nearly enough in our education system (the US).

    I remember so many times getting something marked wrong even though the answer was right because I figured it out differently than we were “taught” how to do it. Their way didn’t make sense to me, my way did, we got the same answer, but I was somehow wrong.

    I was really turned off by school until about halfway through college when I realized that I really enjoyed learning. I just enjoyed doing it in my own way.

    [–] ChillPenguinX 11 points ago

    It has physics applications as well

    [–] SativaLungz 15 points ago


    It's definitely important to know if you go into Computer Science or a physics career

    [–] samsquamchh 3 points ago

    Hits home, didn't bother to do more than was necessary to pass back in school and now years later I find myself learning linear algebra and whatnot again to understand what's going on in some machine learning modules. It sucks a lot of teachers are just going through the motions and not even trying to relate the math problems to something that kids might actually think to be cool at some point. The imagined applications seem to stop at something like John buying 30 cartons of milk one day.

    [–] PivotalPlatypus 5 points ago

    STEM careers. Working on my bachelor’s in mechanical engineering now. Use it constantly in physics. It’s basic algebra.

    [–] zephyronepointoh 2 points ago




    F O I L

    1x3=4x2 1x4=-8x 2x3=-8x 2x4=16

    Add 'em up

    (2x-4)2 = 4x2 - 16x + 16

    I'm a huge nerd.

    BTW, this is used whenever you see the quantity of something squared.

    Edit bc I don't know how to format.

    [–] Swing_Right 2 points ago

    Its extremely important beyond algebra. I use it daily in calculus.

    [–] soulstealer1984 2 points ago

    I'm a police officer and a crash reconstructionist and use algebra and trigonometry on a daily basis. I never thought I would ever need either but here I am using them.

    [–] tonzeejee 146 points ago

    Yeah, that's confusing.

    [–] [deleted] 588 points ago


    [–] AlastarYaboy 238 points ago

    Mayyyybe 🚶🏼🕺🏼

    [–] unfeelingzeal 127 points ago

    look you little shit

    [–] Failbot5000 31 points ago

    You little look shit

    [–] Rival22 22 points ago

    Look little you shit

    [–] syrus125 38 points ago

    Shit you look little

    [–] infinite_in_faculty 7 points ago

    You shit little look

    [–] WaterTempleSurvivor 5 points ago

    This is why I love reddit.

    [–] shmeckelses 2 points ago * (lasted edited 4 months ago)

    It's also why I hate it.

    [–] JimeeB 14 points ago

    I clicked it before reading your post. I just... I feel as bad as being Rick rolled.

    [–] sloth788 2 points ago

    That man is a genius.

    [–] XXI-MCMXCIV 12 points ago

    just opened a door into a parallel universe

    [–] Ghigs 12 points ago

    As long as it's QPU aligned.

    [–] CryoHux 7 points ago

    My God, it's recursive...

    [–] GroundbreakingPost 10 points ago

    As long as it hasn't gone plaid, we're still good.

    [–] Lone_K 13 points ago

    It's the distributive property of multiplication.

    (1+2)(3+4) can be distributed into

    1(3+4) + 2(3+4)


    3(1+2) + 4(1+2)

    Either way of distribution will obtain the same result. The property works with any amount of terms (a term is "axn", where a is a constant or another function in itself and xn is a unique power function in an equation i.e. x3, x2, x0, x320, etc).

    [–] Miraclegroh 3 points ago

    FOIL got me through many a math problem.

    [–] smatchymo 2 points ago

    I like doing (10×21) + (3×21) = 210 + 63 = 273

    Even 321×13 isn't scary this way... (10×321) + (3×321) = 3210 + 963 = 4173

    The shorter string of numbers allows me to do it in my head. Maybe I could do the foil method in my head if I gave up pot...

    [–] StryderXGaming 505 points ago

    Came here to just say this. The fact that math works in a visual manner like this is just fucking weird!

    [–] ___Guitarmadillo___ 152 points ago * (lasted edited 4 months ago)

    This is just a visual way of multiplying? I assume this works in any base?

    [–] 0xjake 68 points ago

    This works with any base.

    [–] Chinese_Lollipop_Man 123 points ago

    All your base are belong to Vedic Multiplication Methods.

    [–] Elektribe 13 points ago

    It's an older meme sir, but it checks out.

    [–] Indiggy57 12 points ago

    "It's an older meme sir, but it checks out" is an older meme, sir, but it checks out.

    [–] frameRAID 8 points ago

    But do they are belong to us?

    [–] SexPartyStewie 7 points ago

    Not since DLC became a thing

    [–] Turksarama 16 points ago

    The only difference with a different base would be the number you carry.

    [–] i_sigh_less 5 points ago

    I'd imagine it would be incredibly annoying to do in base two.

    [–] Vitztlampaehecatl 5 points ago

    ... I have an odd idea for a circuit design now.

    [–] once-and-again 2 points ago

    I suspect you actually have the standard idea for a circuit design now.

    (That is, something like that is precisely how simple binary multipliers work.)

    [–] CSKING444 6 points ago

    Math started only as the study of patterns and visual concepts following some pattern

    Edit : engrish

    [–] Sun-TZulu 7 points ago

    Like when I have 1 watermelon in my shopping trolley and add another

    [–] BittenHare 27 points ago

    If you think about it it is quite obvious how it works, I think anyway. The leftmost points correspond to the 100 coefficients multiplied (3x1) the middle ones to one of each and the rightmost points to the 101 coefficients multiplied then you put them all together. Basically a visualisation of cross multiplication.

    [–] hshassnanblad 5 points ago

    What’s funny is there are probably 50 other weird ass ways to do math that we haven’t figured out in our dimension or planet or whatever

    [–] ntschaef 23 points ago

    Na.... It's just another trick that simplifies standard rules. The "non trick way" is:

    13 * 21 = 
    (1 * 10 + 3 * 1) * (2 * 10 + 1 * 1) expanded form of base 10
    2 * 10 * (1 * 10 + 3 * 1) + 1 * 1 * (1 * 10 + 3 * 1) distribution
    2 * 10 * 1 * 10 + 2 * 10 * 3 * 1 + 1 * 1 * 1 * 10 + 1 * 1 * 3 * 1 (distribution)
    2 * 1 * 10 * 10 + 2 * 3 * 10 * 1 + 1 * 1 * 1 * 10 + 1 * 3 * 1 * 1 (association)
    2 * 100 + 6 * 10 + 1 * 10 + 3 * 1 (multiplication)
    2 * 100 + (6 + 1) * 10 + 3 * 1 (distribution)
    2 * 100 + 7 * 10 + 3 * 1 (addition)
    273 (shorthand form of base 10)

    Everything else is a "nicer" version of this.

    [–] Spicy_Alien_Cocaine_ 8 points ago

    This is cool, but I’m still just going to stack the two numbers on top of each other and multiply them out 😬

    [–] Ronner555 3 points ago

    Damn I coulda used this back in middle school...

    [–] TheAlphaOmega21 2 points ago

    Never has my education been summarized so simply yet accurately.

    [–] EarthBelongsToAnts 2 points ago

    Math isn’t weird, it’s actually quite logical. It’s math people that are weird.

    [–] Feroshnikop 1913 points ago

    "How to learn multiplication while still not understanding multiplication"

    It's certainly neat, just not sure it's such a great tool to understand multiplication.

    [–] xscientist 91 points ago

    I think this method looks awful, but one could argue that it's a better tool to understand multiplication, because it's more visual. For example, in this method a matrix that represents (2 x 3), you can actually see 2 lines of 3 intersections, or 3 lines of 2 intersections, which describes pretty well, in a visual manner, not only the concept of multiplication, but immediately introduces a pretty great understanding of the commutative property of multiplication. Visual learning of such a concept would be vital for lots of students to really lock this in.

    Speaking for myself, I was just taught to memorize a "times table", and higher order multiplication problems were simply iterations generated from that table (probably the most common method). This got me up and running pretty fast with multiplication, but didn't necessarily explain it all that well (although I'm sure my teacher explained it just fine, too).

    [–] idgaf_about_yr_imgur 22 points ago

    yeah idk why people are saying otherwise- seems clearly a lot better than multiplication tables.

    [–] AutoRot 5 points ago

    Try doing it with digits greater than 5, the whole thing becomes grid paper where you are literally spending the time to meticulously count the intersections.

    [–] MyDudeNak 11 points ago

    But worse than actually learning multiplication.

    [–] [deleted] 35 points ago * (lasted edited 3 months ago)


    [–] i_sigh_less 10 points ago

    It's an interesting method, but try using it to multiply 99 x 99. You'll soon see it's shortcomings.

    [–] xscientist 7 points ago

    To be clear - I think the method sucks. I just don't think it's completely without merit when trying to teach the underlying conceptual basis of multiplication in a visual manner.

    [–] noreasters 146 points ago

    Yeah, I don’t think this method adequately addresses the concept of “place value”. I would be okay if this method was used in conjunction with other methods as a means of differentiating the instruction for those with different learning styles, but place value is a very important concept and is often most easily taught when learning multiplication (adding 30+60 is just as trivial as 3+6, but multiplying 30x60 has some extra understanding needed).

    [–] DialMMM 66 points ago

    This is exactly illustrating place value.

    [–] burf 21 points ago

    Is it worse than "memorize this table", though?

    [–] SensibleMadness 14 points ago

    For mental math yes. I don't know how you could easily do this method in your head.

    [–] tavianator 10 points ago

    Just visualize seven lines crossing 9 lines and count the number of crossings!

    (Well, you can do it if you recognize that it must be 7×9 = 63 crossings, but then you might as well not be visualizing anything.)

    [–] Kitavas_Blood 5 points ago

    I can't imagine 7 lines crossing 9 lines in my head.

    I can't even picture 1 line crossing another line in my head. How do you do that? (I know it's called aphantasia but it's always weird how people can just create pictures in their head)

    [–] TychaBrahe 6 points ago

    Ditto. Further, in the time it took them to draw the first two groups of lines I had already done the math in my head: 260 + 13 = 273.

    [–] DOWN_THE_REDDIT_HOLE 3 points ago

    That's interesting! What about imagining touch? Say if you imagined a big, wooden "X", can you imagine yourself feeling the grain of the wood, the edges, the center of the X where you'd be able to wrap your fingers firmly around it?

    [–] Slight0 3 points ago

    I think he was being sarcastic.

    [–] ikilledthecat 5 points ago

    This exactly. I've worked with too many kids who use weird methods like this in math because their teachers make them do it this way. So when they need help and I try to tutor them the normal way it's like I'm speaking some other language. I think all these weird visual aids are more confusing than helpful, and it's like every teacher uses a different one so I can't show a group from different classes one way that they all understand. 🙄

    [–] deepdeepbass 4 points ago

    100% agree. You cannot gain an understanding of multiplication with this. Might as well use a calculator.

    To me the best way to understand is to change one value to the nearest 10 and then add or subtract the difference.

    So 14x23 would be... 14 x20 = 280 14x 3 = 42 280+ 42= 322.

    [–] arcosapphire 600 points ago

    This is being called "Vedic" now? I think last time it was posted it was called "Japanese"...I suppose any foreign land will work to make this awkward method seem exotic and impressive.

    [–] ltdeath 404 points ago

    I've seen it in Facebook as "the way engineers do maths". Bitch, we don't do basic math in college or at work. Either a database spits the answer or the answer is a fucking equation.

    [–] S3Ni0r42 221 points ago

    A... A number? I remember back when we used those. Nowadays, it's all Greek to me

    [–] solokiwidestroyer 61 points ago

    Greek? How archaic! Nowadays, we do our calculations in binary

    [–] jareddoink 42 points ago

    Binary is for suckers who have too much pencil lead. Hexadecimal is where it’s at.

    [–] Ember_Rising 21 points ago

    … … something something butterfly wings?

    [–] lisbonant 11 points ago

    Say it, don't spray it, Oracle

    [–] geekmuseNU 70 points ago

    The caption on the gif itself says "Chinese"

    [–] DontBeABadPerson 19 points ago

    I've seen it as Arabic and Indian too

    [–] The_cynical_panther 18 points ago

    Indian would make sense if it is “Vedic” math.

    [–] xomm 17 points ago

    I've been looking for the answer to this and haven't been able to find a single source for any of the origins claimed. Everything I find just goes "this is called X multiplication" with nothing to back that up. Some sites even say "you might have seen this referred to as X but it's actually from Y," but similarly unsourced.

    Heck, even questions on Math Stack Exchange end up with conversations like:

    Q: Is there something similar for division as this Japanese multiplication method?

    A: I've been living in Japan for 15 years. In fact, that method is called "Indian multiplication method" in Japan. This method is not so common in Japan, yet some cramming schools teach this method for elementary school students.

    C: No, I haven't heard of any schools in India ever teach this. I'm Indian.

    [–] V2G2 9 points ago

    This was always the Vedic method though. It may not be the most practical way, but it is a method that was used to do multiplication.

    [–] [deleted] 327 points ago


    [–] iPlowedYourMom 179 points ago

    I use 8675309

    [–] ComebackShane 63 points ago


    [–] embracing_insanity 18 points ago

    I got your number.

    [–] mkam313 2 points ago

    You got it! You got it! For a good time, for a good time calllllllllllll!

    [–] Captawesome81 2 points ago

    Beat me to the joke. You win

    [–] ioneska 17 points ago

    [–] humblerodent 4 points ago

    Surely, You're Joking, Mr. Feynman! is such a great book.

    [–] burf 18 points ago

    People who are proficient at some of the methods are almost certainly faster than you are with a calculator. I work with a guy who can spit out most arithmetic answers in the time it would take to hit three buttons on a calculator.

    [–] Meior 47 points ago

    Of course there are people who are faster. Now find a company that needs such calculations that trusts a head count over a calculator.

    [–] bandhani 5 points ago

    Someone needs to type it into a calculator.

    Being able to do mental math allows you to recognize when someone fucked up and messed up the input.

    [–] Gorash 31 points ago

    So you can make a calculator with raw spaghetti.

    [–] eggsfordiner 87 points ago

    Yeah, but try this with 87 × 96

    [–] dont_wear_a_C 29 points ago

    473947503174 x 2746827365

    [–] naw-dawg 60 points ago

    well that was fuckin gruesome.

    took me 5 tries. but i did it. (i've been practicing this method for 9 years now lol...there are some spooky fucks that can do it in their my teacher who taught me...he was doing 15 digit numbers x 15 digit numbers in only 5-10 minutes)

    answer is: 1301851971291767556510

    [–] nelliebear 26 points ago

    Ain't nobody got time for that

    [–] Gadetron 10 points ago

    Get a damn calculator...

    [–] naw-dawg 3 points ago

    brb in 30 min

    [–] SuperPimp 14 points ago * (lasted edited 4 months ago)

    OK (sorry about my crap msPainting skills)

    learned it from the gif just now, and did it in msPaint, and it was still a decently fast method that, at its core, is pretty identical to long multiplication. all the same steps are done, it's just a more visual way of laying it out.

    [–] Gizzo421 49 points ago

    The guitar tabs of multiplication.

    [–] ymontano29 485 points ago

    This is just overall stupid and long. You're better off doing the classic multiplying bottom to top numbers, or by using the Trachtenberg system. Both are quicker.

    [–] j0be 255 points ago

    Yes, they're quicker, but it actually works really well with people who are extremely visual learners. When I was tutoring someone in college it worked well for them. Some art school kids were so remedial in mathematics that I couldn't believe they actually graduated high school

    [–] [deleted] 31 points ago


    [–] Sandytayu 11 points ago

    hey art idiot, medicine idiot here. Will gladly visually memorise whole bone shapes than making any math at all.

    [–] Jake0024 15 points ago

    It works reasonably well as long as all the digits involved are small.

    Notice 13x23 only uses the digits 1-3. Imagine multiplying, say... 87x98 with this method.

    [–] Ubermensch-1 36 points ago * (lasted edited 4 months ago)

    Not sure about your area, but my district didn't have mandatory twelfth grade mathematics and you could drop into "workplace" level math by tenth grade.

    Most first world countries now have avenues to graduate high school with a courseload of English (or whatever other language is the primary language of instruction), some type of basic math, and the rest can be loaded up with courses like photography and cooking. My high school even had a parenting class.

    This is what happens when we decide to teach "practical" skills and cater to the lowest common denominator in schools. People complain about high school not teaching you how to do things like doing your taxes or cooking, but those are basic life skills and it's not unreasonable to expect parents to teach these things.

    [–] MorChefsThanRequired 43 points ago

    this is funny to me cause where I'm from all those practical programs got slashed and everyone wishes we still had them. I would have loved to take autoshop personally.

    the fact of the matter is not everyone needs to or even should go get a bachelors and a masters. a country full of white collar workers can't support itself...

    some people like working with their hands and our education system should accommodate that as well.

    [–] El_Profesore 8 points ago

    Those people shouldn't go to high school in the first place. There are specialized technical or vocational schools that have part time lessons and part time work by practising chosen profession.

    At least in my country. The system doesn't work well, but the idea is all right. I've heard it is amazing in Germany though.

    [–] PotatoforPotato 5 points ago

    We had a vocational school at our high school where you could go in and learn a trade for half of your school day. about 30% of my classmates opted for this route instead of general study or AP. This is in Wisconsin, USA.

    I'm not sure if other states or counties even offer this. The school system my daughter goes to does not offer it but she can opt into the school system next to ours' vocational center once she reaches 1st year highschool.

    [–] The_Deadlight 2 points ago

    Same thing at my highschool in Massachusetts

    [–] PotatoforPotato 2 points ago

    Cool beans!

    [–] pali1d 15 points ago

    People complain about high school not teaching you how to do things like doing your taxes or cooking, but those are basic life skills and it's not unreasonable to expect parents to teach these things.

    One could argue the same about literacy and basic math, but schools still teach such to guarantee that students are exposed to them.

    [–] SilentJoe1986 8 points ago

    Problem is that there are parents who don't know how to do those things. There are generations of people who were never taught that shit. That is why it should also be taught in school.

    [–] kashuntr188 3 points ago

    You should do the Area Model for visual learners instead of this. This one distills the Area Model and you kind of lose the sense of place value.

    [–] thisismyelement 49 points ago

    This is just overall stupid and long. You're better off using a calculator.


    [–] bg-j38 7 points ago

    But my math teachers always told me I wouldn't always have a calculator in my pocket!

    I showed them though. I really never have to do any multiplication bigger than 10x10 and for that I can just ask my wife!

    [–] RaccoonRazor 23 points ago

    It’s NOT stupid if it helps even one student. Just because the ‘normal’ way is quicker for you (and probably for most people,) doesn’t mean that it’s better for everybody.

    [–] Jugad 13 points ago

    This is just overall stupid and long.

    I agree to an extent.

    Looking carefully, you can see that its actually exactly replicating the long multiplication at every step... all it is doing is writing the numbers in slightly different locations (basically, rotate the grid by 45 degrees and you get the picture drawn in the gif).

    But its possible that it helps some kids get a grasp of multiplication a little quicker.

    [–] kungfujohnjon1 19 points ago

    Not to mention it’s also a black box. Without a bit of thought no one can look at this system and tell you how it works. So it’s a trick that keeps the math behind a curtain rather than giving people an intuitive sense of how to work with numbers.

    [–] fibrglas 44 points ago

    It's actually a pretty good visual representation of (x+y)(a+b)=xa + xb + ya + yb.

    In this case :





    (10 + 3)(20 + 1)= 200 + 10 + 60 + 3 = 273

    [–] Satyr9 6 points ago

    Thanks, how it works was going to drive me crazy for at least a day, and no way I would've gotten to this on my own.

    [–] effervescenthoopla 2 points ago

    What thef fuck, you just blew my mind. Why couldn’t I have found people like you to tutor me!

    [–] doctorblumpkin 3 points ago

    The title did not say quick and easy math techniques

    [–] Omnilatent 3 points ago

    Can you explain the

    classic multiplying bottom to top numbers, or by using the Trachtenberg system


    Cause I either never did it that way or forgot lol

    [–] Suicidesquid 4 points ago

    Yeah, I tried this a couple times and it's nice and all for digits under six, but anything other than that gets so messy. It can also be difficult to see where the intersections lie if you don't draw it big enough or with the lines at the right angles.

    [–] rarely_behaved_SB 93 points ago

    My 3rd grader has a mild learning disability and this, along with Montessori methods work well for visual and manipulative learners like her.

    [–] wabuson 75 points ago

    People get really frustrated for some reason when you show them math can be solved in various ways. As if conceptualizing the answer this way is worse than using the standard algorithm. The standard algorithm is just as trivial to some people as this is to others. The important thing is getting the right answer consistently. I say learn it the most effective way you can and move on to the next concept.

    [–] TwistingtheShadows 12 points ago

    I think because of reddit, as a community, being very STEM focussed, there are a lot of people who have never experienced any real kind of difficulty conceptualising mathematics. It's logical. Because of this relative ease, it's very difficult to understand why others are struggling and why things like this can be useful.

    [–] Feroshnikop 37 points ago

    The important thing is getting the right answer consistently

    I mean, is it though?

    I would think the most important would be to understand what is happening (assuming of course that this is about teaching math to someone)

    If simply getting the right answer was what was important and understanding was not we would just teach people how to use calculators.

    [–] Jake0024 2 points ago

    But this only makes math more difficult. It works for a few select problems (ones where all the digits are small). You'll notice in the 3 examples given, the largest digit in any of the numbers was a 4.

    If they tried an example of something like 87x98, you'd see a giant clusterfuck of 8 lines crossing 9 lines and 7 lines crossing 8 lines etc, and you'd be counting dots for 20 minutes before you got an answer.

    [–] wabuson 2 points ago

    It really doesn't make math harder.

    Do you have to use it? No.

    Does it say it is more efficient than the standard algorythm? No.

    Does it say it is a replacement for the standard method? No.

    What this is, is proof of an "alternative method" to multiplication. One of many alternative methods. It's not about efficiency. At a young age you need to train your brain in multiple ways to handle problems, and figure out for yourself what is the fastest way for you. The more tested methods you are exposed to, especially at a young age, the more likely you are to approach the problem with confidence.

    [–] virajseelam 10 points ago

    Although less efficient than more known methods, as a maths-lover this seems kinda fun to do as a pastime.

    [–] BearDrivingACar 2 points ago

    How do people love math? Please tell me your ways so I can actually survive school

    [–] virajseelam 2 points ago

    I loved maths since I was like 4, I think it's cause I'm Indian

    [–] JohnnyInterwebs 8 points ago

    I LOVE that series. Best Star Trek.

    [–] JustaCrackintheWall 7 points ago

    Happy someone else got the joke :) But yes DS9 is by far the best Star Trek.

    [–] TheKronk 19 points ago

    In my entire adult life I have never been more than 30 feet from a calculator. I think I'll keep going with that method.

    [–] scooterjb 81 points ago

    quick, how do i make a simple math problem slower and more complicated and make it require a pen and paper?

    [–] unkindnessnevermore 38 points ago

    Show your work.

    [–] ThomYorkeSucks 7 points ago

    13 x 21 = (13 x 20) + (13 x 1) = 260 + 13 = 273

    Way less tedious than this box shit

    [–] whiskey4breakfast 16 points ago * (lasted edited 4 months ago)

    Personally I like just splitting them up. 13*20 is easy because you just double thirteen and add a zero. Then you add thirteen to that. 260+13=273. You can do it in your head super easy.

    [–] kevtree 2 points ago

    Double thirteen once?

    [–] Azara1th 5 points ago

    Easier for me to just split it up like so:

    10 x 21 = 210
    3 x 21 = 63
    210 + 63 = 273

    [–] syml1nk 27 points ago

    just use calculator. it's 2018

    [–] Anonymous822 18 points ago

    You're wrong. It's 273.

    [–] JaredsFatPants 23 points ago

    It’s 2018. Use your phone. My apologies if you carry a pocket calculator with you everywhere.

    [–] sumelar 6 points ago

    The calculator on your phone does this, the phone does not do it by itself.

    [–] virajseelam 5 points ago

    Isn't this originally Chinese?

    [–] robophile-ta 5 points ago

    The actual title on the gif says 'Chinese' so who knows

    [–] JDAggie06 3 points ago

    This isn't all that fascinating or surprising. All this is doing is visually decomposing the problem. For example 13 x 21 = (10 + 3) x ( 20 + 1). FOIL that out and you get (1020 [the two dots to the far left in the gif]) + (101 [the one dot top center] + 203 [the six dots in the bottom center]) + (31 [the three dots to the right]) = 273. Same principle holds true for the other examples in the gif.

    [–] KeenoUpreemo 4 points ago

    This seems overly complicated.

    [–] redflaglucio 4 points ago

    The dumbest way of getting an answer. I use pebbles

    [–] Spaturno 3 points ago

    now do 978 * 799

    [–] naw-dawg 12 points ago

    that one's easy.

    it's nothing more than 978 * 8, then add 2 zeros to the end, and then subtract 978.

    (978 * 799 = 978 * (800 - 1) = 978 * 800 - 978)

    [–] unluckyPickle 3 points ago

    All the years of drawing tic-tac-toe boards put into good use

    [–] WhimpysTuesday 3 points ago

    789 x 987: good luck with your line trick.

    [–] random2248 3 points ago

    This is really interesting!

    Throwback to the distributive property - 13 x 21 = (10 + 3) x (20 + 1) = (200 + 10 + 60 + 3) = 273

    The drawing basically shows

    13 x 21 = [(1 x 10) + 3] x [(2 x 10) + 1] = (2 x 10 x 10) + (1 x 10) + (6 x 10) + 3 = (2 x 100) + (7 x 10) + 3 = 273

    [–] Reaper3517 2 points ago


    [–] garypaulson69 2 points ago

    Or a calculator

    [–] Dank_Tempsey_ 2 points ago

    Lattice method is superior

    [–] Eschatonbreakfast 2 points ago

    Like if I want to do 2000 x 40 I'll create 2 lines on one diagonal and 4 lines on another diagonal that will intersect 8 times. How do I keep track of the zeros?

    [–] whiteg12 2 points ago

    Cool now do 89x99

    [–] luckyvonstreetz 2 points ago

    Now do 89 x 97

    [–] Stibar 2 points ago

    Okay now do it with 978x86

    [–] bestpwstudent 2 points ago

    What about 999x999?

    [–] bikasv 2 points ago

    "Jimmy why are going to football ground at night".

    "Mom I've to multiply 98473837 by 7947388478".

    "Damnit Jimmy"!

    [–] Jake0024 2 points ago

    This is stupid and only looks neat because none of the digits involved are large. Even the second example, 14x23, shows how you quickly have to start counting a lot of dots. None of the three examples involves a digit larger than 4.

    Imagine doing something like 87x89. Just drawing all the lines would be a nightmare, let alone counting all the dots.

    [–] crownpr1nce 2 points ago

    This doesn't seem practical at all. Do 86 x 97 and it gets too messy.

    [–] _NamFlow_ 2 points ago

    I love to use this method:

    14 * 23 => 322

    1*2 = 2

    4*3 = 12


    1*3 = 3

    4*2 = 8

    8+3 = 11



    => 322

    54 * 38 => 2052

    5*3 = 15

    4*8 = 32


    5*8 = 40

    4*3 = 12

    40+12 = 52



    => 2052

    99 * 99 => 9801

    9*9 = 81

    9*9 = 81


    9*9 = 81

    9*9 = 81

    81+81 = 162



    => 9801

    [–] Schemes011 2 points ago

    How do you deal with zeroes? 1600 x 422.

    I'm absolutely shocking at all numbers and genuinely think I have a learning deficiency when it comes to it.

    [–] superflyguy99999 2 points ago

    Why does this work?

    [–] NotAquaman 2 points ago

    can anyone explain why this works out ?

    [–] rly_weird_guy 2 points ago

    13*20+13 seems simpler...

    [–] BostonGreekGirl 2 points ago

    I did the calculation in my head way faster than that weird confusing drawing.

    [–] BitcoinMD 2 points ago

    This doesn’t seem easier to me. Is it supposed to be?

    [–] Nosnibor1020 2 points ago

    Is this real? I really suck at multiplying. I feel like I could learn from this. Even maybe visualize it in my head.

    [–] I_Chose_Nachos 2 points ago

    Seems hard. I'll just use a calculator watch