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Amazing Math Trick Schools Don't Teach - Egyptians/Russian Peasant Method

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You can multiply two numbers if you know how to double, halve, and add up numbers. This is really interesting: basically the Egyptians were using binary multiplication! Watch the video to see how it works. READ why this method works: http://mindyourdecisions.com/blog/2014/08/27/the-egyptian-method-russian-peasant-multiplication-video-and-a-proof/#.U_5I5vldV8E WATCH how ancient Egyptians divided numbers: https://www.youtube.com/watch?v=bKqQGISplMo This method is documented in the Rind Mathematical Papyrus. The document is from ~1650 BC, which is more than 3,600 years ago. Rind Mathematical Papyrus: http://en.wikipedia.org/wiki/Rhind_Mathematical_Papyrus Here's a book with more info about non-western mathematical history, "The Mathematics of Egypt, Mesopotamia, China, India, and Islam: A Sourcebook" : http://amzn.to/1CuroWL If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is most convenient for you. My Blog: http://mindyourdecisions.com/blog/ Twitter: http://twitter.com/preshtalwalkar Facebook: https://www.facebook.com/pages/Mind-Your-Decisions/168446714965 Google+: https://plus.google.com/108336608566588374147/posts Pinterest: https://www.pinterest.com/preshtalwalkar/ Tumblr: http://preshtalwalkar.tumblr.com/ Instagram: https://instagram.com/preshtalwalkar/ Patreon: http://www.patreon.com/mindyourdecisions Newsletter (sent about 2 times a year): http://eepurl.com/KvS0r My Books "The Joy of Game Theory" shows how you can use math to out-think your competition. (rated 4/5 stars on 23 reviews) https://www.amazon.com/gp/product/1500497444 "The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" is a handbook that explains the many ways we are biased about decision-making and offers techniques to make smart decisions. (rated 5/5 stars on 1 review) https://www.amazon.com/gp/product/1523231467/ "Math Puzzles Volume 1" features classic brain teasers and riddles with complete solutions for problems in counting, geometry, probability, and game theory. Volume 1 is rated 4.5/5 stars on 11 reviews. https://www.amazon.com/gp/product/1517421624/ "Math Puzzles Volume 2" is a sequel book with more great problems. https://www.amazon.com/gp/product/1517531624/ "Math Puzzles Volume 3" is the third in the series. https://www.amazon.com/gp/product/1517596351/ "40 Paradoxes in Logic, Probability, and Game Theory" contains thought-provoking and counter-intuitive results. (rated 4.9/5 stars on 7 reviews) https://www.amazon.com/gp/product/1517319307/ "The Best Mental Math Tricks" teaches how you can look like a math genius by solving problems in your head (rated 4.7/5 stars on 3 reviews) https://www.amazon.com/gp/product/150779651X/ "Multiply Numbers By Drawing Lines" This book is a reference guide for my video that has over 1 million views on a geometric method to multiply numbers. (rated 5/5 stars on 1 review) https://www.amazon.com/gp/product/1500866148/
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Text Comments (65)
12*13 Not applied.. Pls solve
でんきパワー (1 month ago)
you forgot to cross the first row 12*13 because 12 is even so the answer is 156
Georgios Ivankof (6 months ago)
It's too long.
Ashutosh shreyan (7 months ago)
It takes as long time as to multiply as a simple way if u r not satisfied then apply
Ashutosh shreyan (7 months ago)
With the help of binary system
Pantokrator (7 months ago)
Doesn't work for 17x23.
でんきパワー (1 month ago)
17 * 23 8 46 cross 4 92 cross 2 184 cross 1 368 23+368=391 It`s right
ГОЛУБЬ НАТАША (11 months ago)
Это нахождение НОК?
ГОЛУБЬ НАТАША (11 months ago)
artemetra хых. Тут их много Только в переводчике пишут.
artemetra (11 months ago)
Женя Архипова дудки. Это попросту трюк будто легче находить. (Я даже не поверил что здесь кушать российские лол)
nicole Regan (11 months ago)
This is 1000X easier to understand than how my teacher taught us! I was about to pull my hair out. Thank you!
Christian Gingras (1 year ago)
That is amazing how "primitives" people were doing binary while modern software engineer barely understand how the computers they program perform multiplication in their native electronic circuits. Many microcontrollers don't even perform multiplication. A software must loop thru these division by 2 (binary shift right), test the bit that shift just discarded (bit "Carry" == 1?), if yes, proceed to doubling (add register r1 to register r1, store result in same r1)... That is all a processor do millions of times to simulate any other operation... Exponential, sin, log, etc... Almost.
Márton Németh (1 year ago)
In the video. 'space' Description. :)
Ty bot (1 year ago)
I've always gone a different even more confusing route, basically working from 10's or 5's 8x7=(40)+(8x2) or (+8+8) or (80)-(3x8) or (-8-8-8) I'll never ever remember specific numbers in multiplication, but I know that all numbers go up in 10s or that there's a pattern, so I'll break down basically any equation into a couple more manageable additions but using that pattern. It's really stupid on paper but it works really well for me, and I almost never have to write anything down except maybe a couple numbers for larger equations. If someone asks me what 38x16 is, I have no idea, but I know 38x10 is definitely 380, and that half of 380/5x38 is definitely 190, so the answer has to be 380+190+38 or 608
Lord Helixus (1 year ago)
That's how I have and always will multiply.
Night Falls (1 year ago)
This is witchcraft!
Ahmed Saber (1 year ago)
Dos it works only for any boucle digits ?
Charles Bryan (1 year ago)
doesn't work with 25 x 91.
Mycroft616 (1 year ago)
It does: 25 x 91 12 x 182 (ignore) 6 x 364 (ignore) 3 x 728 1 x 1456 91 + 728 + 1456 = 2275 It's far more complicated than just multiplying left to right, as well as breaking up 91, but it does work for 25 x 91.
DaAwesomePossum (1 year ago)
It doesn't work for me If I multiply 13 by 24, I get 312 But if I multiply 24 by 13 I get 325😂 I think it might be because it doesn't have remainders so it is not equal.
でんきパワー (1 month ago)
+Funny Angel you should look at the first number 24 is even so cross the row
Funny Angel (11 months ago)
Jiiks but if both number aren‘t even, you aren‘t allowed to remove that row. No metter if the lower number is put at first or not.
Funny Angel (11 months ago)
Jiiks but maybe, you must put the lower number first if it isn‘t a even number. So if you still want to put the lower not even number at the end, you must remove it at the end, even if it‘s not a even number:D
Funny Angel (11 months ago)
Jiiks but 24*13 isn‘t an even number row, is it?
xx xx (1 year ago)
6 months late but good job.
XxbravesxX 239 (2 years ago)
Oh my gosh it JB
Meta tron (2 years ago)
Why is 1/2 of 13 6?
Dan Mang (1 year ago)
13 / 2 is 6.5 which becomes 6 without a remainder.. 3 / 2 is 1.5 which becomes 1 without remainder
rosacute jenniely (1 year ago)
How do you do that? WHAT IS THE REMAINDER? Whyd he keep the one if he got rid of the other two???
tony1509 (2 years ago)
we ignored the reminder
Akash Mangal (2 years ago)
Bros I even have a more convinient way to multiply any combination of numbers not just two, but for two it works smoothly. 13x69 (say) First just multiply the right hand part vertically 4x3=12 Put it at right part of answer (just 2, 1 will be carried) Cross multiply 1x4 and 6x3 and add which becomes 22 Add 1 and it becomes 23 Put it as middle part of answer (just 3, 2 carried) Finally multiply 6x1 of left part vertically and add 2 to it. 1 3 X 6 4 ------ 832 At first reading it may look a bit grossy but when you do a little in paper you will realise and ya it is not like the traditional method of writing two numbers and then adding. Its a one line answer indeed. By the way it is called "Urdhva Tirayak" method which means vertically and cross wise.
Dan Mang (1 year ago)
it's confusing how you first say 69 then start talking about 64
Awesome in Blossom (2 years ago)
Music4Worship (2 years ago)
I tried this with 52x25. Help me with this.
+Phantom King When to switch no's... Any rule for this
Dan Mang (1 year ago)
41 .. 27 20 .. 54 10 .. 108 5 .. 216 2 .. 432 1 .. 864 27 + 216 + 864 = 1107 41 x 27 = 1107
Phantom King (2 years ago)
I tried it with 41x 27 but it came out wrong but when I did 27 x 41 it came out right
Phantom King (2 years ago)
so 25X52
Phantom King (2 years ago)
try switching the numbers around
YellowBunny (2 years ago)
So this is basically just binary multiplication in the decimal system. What's special about that? Edit: Okay you say that, didn't watch the whole video :D
Jose Villegas (2 years ago)
So the ancient egyptians were treading on a mathematical path that leads to binary numbers. That's very interesting indeed.
dark plays (1 month ago)
mz [ Matt.a .
Forty Two (3 years ago)
I came up with this style of multiplication in 3rd grade because it made it easier for me, turns out it wasn't so original!
Kai Mm (1 year ago)
That's impressive!!! I'm so stupid that I cannot do that by my own! :)
Jose Villegas (2 years ago)
+Forty Two still that's really impressive
eds floresca (4 years ago)
It doesnt work huhu... Or maube I dunno how to do it... 12 x 16 6 32 (cross out) 3 64 (cross out) 1 128 _____________ 144 Answer: 192
iiFraXure (7 months ago)
u crossed out the uneven number.
Michael Empeigne (2 years ago)
cross out any rows that begin with an even number; then you are left with : 3.........64 1........128 Now add the numbers on the right : 64 + 128 = 192
Abdullah Mansoor (3 years ago)
+eds floresca You have to cross out even rows 12 x 16 (cross out) <---- Both sides even 6 32 (cross out) <---- Both sides even 3 64 <---- Both sides not even 1 128 <---- Both sides even ___________ 192 64 + 128 = 192
MindYourDecisions (4 years ago)
+Son Resca Cross out any rows that begin with an even number. For your problem 12 x 16 6      32 3      64 1      128 You cross out the rows starting with 12 and 6. 3      64 1      128 Then you add 64 +128 = 192.
eds floresca (4 years ago)
+stormruston i misunderstood what to cross out. Please teach me.
eds floresca (4 years ago)
It doesnt work huhu... Or maube I dunno how to do it... 12 x 16 6 32 (cross out) 3 64 (cross out) 1 128 _____________ 144 Answer: 192
Kip K (1 year ago)
Abdullah Mansoor yes
Musical Inquisitor (1 year ago)
+eds floresca Cross out any rows that begin with an even number. For your problem 12 x 16 6 32 3 64 1 128 You cross out the rows starting with 12 and 6. 3 64 1 128 Then you add 64 +128 = 192. If you're going to copy and paste don't use an already proven answer from the guy who used the method and understood it (well enough).
Abdullah Mansoor (3 years ago)
+eds floresca You have to cross out even rows 12 x 16 (cross out) <---- Both sides even 6 32 (cross out) <---- Both sides even 3 64 <---- Both sides not even 1 128 <---- Both sides even ___________ 192 64 + 128 = 192
PigletCNC (4 years ago)
It may work but it's sooooooooooooooooooooooooooooooooooooooooo much more complicated.
Madder of the Few (1 year ago)
Try the Lattice method. It's sooooooooooooooooooooooo much easier than the traditional way. The only skill it requires is addition, and it also works when one of the numbers is a decimal.
lobsterbark (1 year ago)
How is it more complicated? This is easy, I learned it and understood it well enough to use it just watching this video, and it only requires you to remember three or four numbers at a time. It's extremely fast, neat, and can be used practically with numbers of up to a dozen digits or so. Memorizing tables is a stupid waste of time because if you don't constantly practice you will lose it, and if you have a job where you multiply smaller numbers together often enough for it to be useful you will naturally learn it without trying anyways. The traditional method requires you to remember seven or eight numbers at a time, which is rediculous. It's like having to memorize a different telephone number every time you need to do basic multiplication, and it leads to mistakes that could easily be avoided by using a better method.
columbus8myhw (1 year ago)
Whatever you're used to feels easiest
Lightdeaf (2 years ago)
+PigletCNC That means ancient egyptians were very smart
Chris Mitchell (4 years ago)
This is incredible, I can't believe that this actually works!
Jonathan L (4 years ago)
thats really cool! great vid man!

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