crazy russian math technique - video

That is interesting. I'm going to show the video to my kid to see if she can pick it up.

That is crazy... I'm going to leave this up. It's kind of spamish, but really interesting. I don't know what the title says so I'll edit it.

That is awesome. Any mathematicians on here? Why does it work? Does it only work when the two number you're multiplying have the same number of digits? What if one of the numbers has zeros in it?

I just did it with zeroes, it works. You don't even have to count the dots, just do smaller sets of multiplication. I'd like to know how someone came up with that, but it's really sweet.

Cool. I'm a visual learner. I understand how it works, but I can't really explain it. Fundamentally, there's really no difference in doing it the long hand way vs. graphically. I didn't know this technique existed, I'll try to use it from now on.

My lame attempt to explain this. For example we need to calculate 12 x 14 = I broke it down to (10 + 2) x (10 + 4) = 100 + (20 + 40) + 8 Draw the lines according to the method, you'll see that the number of points in each region corresponds to the broken down equation I did above: a. 2 lines intersect makes 1 point, since these 2 lines represent the first digit (1) of the 12 and 14 number, they correspond to 10 x 10, put the number of points down as the first digit of your result b. 4 lines intersect 1 line makes 4 points, since these 4 lines represent the second digit (4) of the number 14, they correspond to 10 x 4 c. 2 lines intersect 1 line makes 2 points, since these 2 lines represent the second digit (2) of the number 12, they correspond to 10 x 2 + add both the number of points found in b. and c. to get the second digit of your result d. 2 lines intersect 4 lines makes 8 points, just like 2 x 4, since these 2 lines and 4 lines both represent the second digits of number 12 and 14 respectively, they correspond to 2 x 4 write down the number of points found in d. as the last digit of your result. The key to this method is line intersection, x number of parallel lines intersect at a right angle with y number of parallel lines gives us a total of x * y number of points

That's cool as hell. A weird thing to get spammed... Nice explanation too, Metkirk.

see metkirk - yet another reason why college isnt a complete waste of your time! Thanks for the explanation cool piece of spam

Yeah, as I was explaining it to friends last night, I pretty much figured it out why it works. Then we got into a discussion about how the last cold war slide rule in Russia finally broke so they had to make this multiplication method up, and that they had just finished building a computer to comete with the WOPR from the movie War Games, etc.

that's like magic. i wonder if i can do it faster than longhand multiplication...or if i can do it in my head. i'm going to practice and find out.

I never thought I would read those words one day and actually agree...

eh, i'd rather use a calculator

It's super cool, but I can still do the longhand version 10 times faster. I'm slightly OCD, so I have to make all the lines are really straight.